可使用以下程式碼：

//Create our own namespaces for the output
XmlSerializerNamespaces ns = new XmlSerializerNamespaces ();
 //Add an empty namespace and empty value
ns.Add ("", "");
 //Create the serializer
XmlSerializer slz = new XmlSerializer (someType);
 //Serialize the object with our own namespaces (notice the overload)
 
slz.Serialize (myXmlTextWriter, someObject, ns);

此外，在評論中還提到了去除開頭的<?xml version="1.0" encoding="utf-8"?>的方法：

XmlWriterSettings settings = new XmlWriterSettings ();
 // Remove the <?xml version="1.0" encoding="utf-8"?>
settings.OmitXmlDeclaration = true;
 XmlWriter writer = XmlWriter.Create ("output_file_name.xml"
 
, settings);
 
另外，如果出現開頭沒有encoding="utf-8"時，應該使用：
 XmlWriterSettings settings = new XmlWriterSettings ();
settings.Encoding = Encoding.UTF8;
 XmlWriter writer = XmlWriter.Create ("output_file_name.xml", settings);