1.在Unity 檔案目錄下找到 system.Drawing.dll ,把它放在Assets 目錄下

2. 在PlayerSetting 把.Net2.0 換成 Net4.0

3.

using System;
using System.Collections;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using UnityEngine;

public class PlayGif : MonoBehaviour
{

    public
 
 bool OnecState = false;
    public bool loopState = false;
    public UnityEngine.UI.Image Im;
    public string gifName = "";
    public GameObject[] Ims;
    [SerializeField]
    private float fps = 5f;
    private List<Texture2D> tex2DList = new List<Texture2D>();
    private float time;
    Bitmap mybitmp;
    
 
void Start()
    {
        System.Drawing.Image image = System.Drawing.Image.FromFile(Application.streamingAssetsPath + "/" + gifName + ".gif");
        tex2DList = MyGif(image);
    }

    // Update is called once per frame
    void Update()
    {
        if (tex2DList.Count > 0&&(OnecState || loopState))
        {
            time 
 
+= Time.deltaTime;
            int index = (int)(time * fps) % tex2DList.Count;
            if (Im != null)
            {
                Im.sprite = Sprite.Create(tex2DList[index], new Rect(0, 0, tex2DList[index].width, tex2DList[index].height), new Vector2(0.5f, 0.5f));
            }
            if (Ims.Length != 0)
            {
                for (int i = 0; i < Ims.Length; i++)
                    Ims[i].GetComponent<Renderer>().material.mainTexture = tex2DList[index];

            }

            if (index == tex2DList.Count-1)
            {
                OnecState = false;
                time = 0;
            }
                
        }
    }
    private List<Texture2D> MyGif(System.Drawing.Image image)
    {

        List<Texture2D> tex = new List<Texture2D>();
        if (image != null)
        {

            //Debug.Log("圖片張數：" + image.FrameDimensionsList.Length);
            FrameDimension frame = new FrameDimension(image.FrameDimensionsList[0]);
            int framCount = image.GetFrameCount(frame);//獲取維度幀數
            for (int i = 0; i < framCount; ++i)
            {

                image.SelectActiveFrame(frame, i);
                Bitmap framBitmap = new Bitmap(image.Width, image.Height);
                using (System.Drawing.Graphics graphic = System.Drawing.Graphics.FromImage(framBitmap))
                {
                    graphic.DrawImage(image, Point.Empty);
                }
                Texture2D frameTexture2D = new Texture2D(framBitmap.Width, framBitmap.Height, TextureFormat.ARGB32, true);
                frameTexture2D.LoadImage(Bitmap2Byte(framBitmap));
                tex.Add(frameTexture2D);
            }
        }
        return tex;
    }
    private byte[] Bitmap2Byte(Bitmap bitmap)
    {
        using (MemoryStream stream = new MemoryStream())
        {
            // 將bitmap 以png格式儲存到流中
            bitmap.Save(stream, ImageFormat.Png);
            // 建立一個位元組陣列，長度為流的長度
            byte[] data = new byte[stream.Length];
            // 重置指標
            stream.Seek(0, SeekOrigin.Begin);
            // 從流讀取位元組塊存入data中
            stream.Read(data, 0, Convert.ToInt32(stream.Length));
            return data;
        }
    }
}