JS端。檔案過大，開始使用了壓縮檔案後上傳。後面改為分段上傳，壓縮檔案部分沒有做對應修改。

       jx: function () {

                if (!$("#SearchForm").form('validate')) {
                    return false;
                }
                var filepath = $("#importExcel").val().trim();
                var laststr = filepath.substr(filepath.lastIndexOf("
 
."));
                if (filepath == "") {
                    $.messager.alert('提示資訊', '請選擇要匯入的檔案！');
                    return;
                }
                else if (laststr != ".xls" && laststr != ".xlsx") {
                    $.messager.alert('提示資訊', '檔案型別傳入錯誤，請選擇Excel檔案！');
                    
 
return;
                }


                //var formData = new FormData();
                //formData.append("fileName", document.getElementById("importExcel").files[0].fileName);
                $.messager.progress({ 'text': '載入中', showType: 'fade' });//呼叫前開啟
                var excelFile = document.getElementById("
 
importExcel").files[0];
                var reader = new FileReader();
                reader.readAsDataURL(excelFile);
                reader.onload = function () {
                    var start = "data:application/vnd.ms-excel;base64,";//獲得字串的開始位置
                    var strBase64 = reader.result.substring(start.length);

                    var zip = new JSZip();
                    // 向zip檔案中新增圖片，可以新增多個檔案或者圖片，此處以圖片為例
                    // base64圖片需要去掉base64圖片標識
                    zip.file(excelFile.name, strBase64, { base64: true });
                    zip.generateAsync({
                        type: "base64",  // 壓縮型別
                        compression: "DEFLATE",      // STORE：預設不壓縮 DEFLATE：需要壓縮
                        compressionOptions: {
                            level: 9  // 壓縮等級1~9    1壓縮速度最快，9最優壓縮方式
                            // [使用一張圖片測試之後1和9壓縮的力度不大，相差100位元組左右]
                        }
                    }).then(function (content) {

                         
                        var allSize = content.length;
                        var fromSize = 0;
                        var ToSize = 0;
                        var updSize = 50 * 1024;

                        var paga = parseInt(((parseInt(allSize) / parseInt(updSize)) + 1));

                        var isOver = false;
                        var isAsync = false;//最後一次用非同步處理
                        var txtFileName = new Date().getTime() + ".txt";
                        $.messager.progress({ 'text': '載入中', showType: 'fade' });//呼叫前開啟

                        for (var i = 0; i < paga; i++) {

                            fromSize = i * updSize;
                            ToSize = (i + 1) * updSize;

                            if ((parseInt(fromSize) + parseInt(updSize)) > parseInt(allSize)) {
                                 
                                isOver = true;
                                isAsync = true;
                                ToSize = allSize;
                            }

                            var blobcontent = content.slice(fromSize, ToSize);
                            // 壓縮的結果為blob型別（二進位制流）,可用作檔案上傳
                           
         
                            $.ajax({
                                url: "/EKBMS/PrdctPlansUpload/ImportLoan1026",
                                async: isAsync,//預設是true：非同步，false：同步。
                                type: 'POST',
                                data: { "fileExcelName": excelFile.name, "strBase64": blobcontent, "isOver": isOver, "txtFileName": txtFileName, "IndexCtn": i },
                                //data: { "fileExcelName": excelFile.name, "strBase64": blobcontent },
                                beforeSend: function () {
                                    //$.messager.progress({ 'text': '載入中', showType: 'fade' });//呼叫前開啟
                                },
                                success: function (res) {
                                     
                                    if (!isOver) return;

                                    if (res.Result) {
                                        document.getElementById("ImportLoanform").reset();
                                        $('#export').dialog('close')
                                        $.messager.progress('close');//回撥後關閉
                                        var Msg = res.Msg;
                                        $.messager.alert('提示資訊', Msg);

                                        //匯入成功後重新整理頁面資料
                                        GetData();
                                    }

                                    else {
                                        $.messager.progress('close');//回撥後關閉
                                        //執行解析失敗
                                        var Msg = res.Msg;
                                        $.messager.alert('提示資訊 ', Msg);
                                        //$("#SearchForm")[0].reset();
                                    }

                                },
                                complete: function () {
                                     
                                    if (!isOver) return;
                                    $.messager.progress('close');//回撥後關閉
                                },
                                error: function (er) {
                                     
                                    if (!isOver) return;
                                    $.messager.progress('close');//回撥後關閉
                                    $.messager.alert('提示資訊', '操作失敗！');
                                    // $("#SearchForm")[0].reset();
                                }
                            });


                            if (isOver) break;
                        }

                    });
                };
                reader.onerror = function (ex) {
                    console.log("上傳失敗", ex)
                }

                //var xhr = new XMLHttpRequest();
                ////post方式，url為伺服器請求地址，true 該引數規定請求是否非同步處理。
                //xhr.open("post", "/PrdctPlansUpload/ImportLoan", true);

                ////請求完成
                //xhr.onload = this._uploadComplete;
                ////請求失敗
                //xhr.onerror = this._uploadFailed;

                ////開始上傳，傳送form資料
                //xhr.send(formData);
            },

Controller端

        /// <summary>
        /// 匯入EXCLE
        /// </summary>
        /// <param name="importExcel"></param>
        /// <returns></returns>
        public JsonResult ImportLoan1026(string fileExcelName, string strBase64, bool isOver, string txtFileName, int IndexCtn)
        {

            //_Service.AddSysLog(ModuleCode.PrdctPlansUpload, OperateCode.Import, LogFlag.INFO, "進入方法ImportLoan成功!操作者：" + LoginUser.UserNo + "檔案是否為空" + (importExcel == null).ToString(), null);

            string FilePath;


            FilePath = Server.MapPath("~/Excel") + "\\" + txtFileName;
            if (IndexCtn == 0)
            {
                System.IO.File.Create(FilePath).Close();
            }
            //寫入內容
            FileStream fs = new FileStream(FilePath, FileMode.Append);
            StreamWriter sw = new StreamWriter(fs);
            sw.WriteLine(strBase64);
            sw.Close();
            fs.Close();


            //如果不是最後一個，則在系統存一個零時txt，儲存內容
            if (!isOver)
            {  
                return Json(new ResultPageModel<PrdctPlansImportModelVM> { Result = false, rows = null, Msg = "繼續上傳!" });
            }


            //讀取檔案  
            strBase64 = string.Empty;
            FilePath = Server.MapPath("~/Excel") + "\\" + txtFileName; 
            StreamReader sr = new StreamReader(FilePath, Encoding.Default);
            String line;
            while ((line = sr.ReadLine()) != null)
            {

                strBase64=strBase64+line.ToString(); 
            }
            sr.Close(); 

            List<PlanAllONE> lstPlan = new List<PlanAllONE>();
            PlanAllVM _PlanAllVM = new PlanAllVM();
            bool _IsSuc = true;
            string _Msg = string.Empty;
            List<PrdctPlansImportModelVM> LisPrdctPlan = new List<PrdctPlansImportModelVM>();
            try
            {

                if (string.IsNullOrEmpty(strBase64))
                {
                    RespModel.WarningResult("上傳的檔案不能為空");
                    //return Json(RespModel, "text/html", JsonRequestBehavior.AllowGet);
                    return Json(RespModel);
                }

                //將字串轉換為byte陣列
                byte[] bytes = Convert.FromBase64String(strBase64);
                var filePath = Server.MapPath("~/Excel");
                var fileName_Zip = filePath + "\\" + fileExcelName.Substring(0, fileExcelName.IndexOf(".")) + ".Zip";
                Bytes2File(bytes, filePath, fileExcelName);
                var fileName_Excel = string.Empty;
                //解壓   
                UnpackFiles(fileName_Zip, filePath + "\\ExcelXLS", ref fileName_Excel);

                // 開啟檔案
                FileStream fileStream = new FileStream(fileName_Excel, FileMode.Open, FileAccess.Read, FileShare.Read);
                // 讀取檔案的 byte[]
                byte[] bytes_New = new byte[fileStream.Length];
                fileStream.Read(bytes_New, 0, bytes_New.Length);
                fileStream.Close();
                // 把 byte[] 轉換成 Stream
                Stream stream = new MemoryStream(bytes_New);
                //刪除檔案
                ExcelDel(fileName_Zip);
                ExcelDel(fileName_Excel);
                ExcelDel(FilePath);

               
                return Json(new ResultPageModel<PrdctPlansImportModelVM> { Result = _IsSuc, rows = LisPrdctPlan, Msg = _Msg });
                //return Json(new ResultPageModel<PrdctPlansImportModelVM> { Result = _IsSuc, rows = LisPrdctPlan, Msg = _Msg }, "text/html", JsonRequestBehavior.AllowGet);
            }

            catch (Exception ex)
            {
                _Service.AddSysLog(ModuleCode.PrdctPlansUpload, OperateCode.Import, LogFlag.ERROR, "匯入的模板格式不正確,資料異常!", ex);
                //return Json(new ResultPageModel<PrdctPlansImportModelVM> { Result = false, rows = LisPrdctPlan, Msg = "匯入異常!" }, "text/html", JsonRequestBehavior.AllowGet);
                return Json(new ResultPageModel<PrdctPlansImportModelVM> { Result = false, rows = LisPrdctPlan, Msg = "匯入異常!" });
            }


        }