string flashSrc = "e:\\t.swf";
StringBuilder sb = new StringBuilder();
sb.Append("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 Transitional//EN\">");
sb.Append("<HTML><HEAD></HEAD><BODY style=\"margin:0; padding:0;\">");
sb.Append("<embed style=\"POSITION:absolute;\" align=\"center\" src=\"" + flashSrc + "\" width=\"100%\" height=\"100% \" type=\"application/x-shockwave-flash\" wmode=\"transparent\" quality=\"high\"></embed>");
sb.Append("</BODY></HTML>");
webBrowser1.DocumentText = sb.ToString();
webBrowser1.IsWebBrowserContextMenuEnabled = false;
原文：http://www.cnblogs.com/flyrain/p/winform_webflash.html