在网上查找了大半天终于解决了，也不知道对不对，反正问题是解决了，网上大部分都是说使用vue axios代理设置，一直没配置成功，最后修改的后端global.asax文件，解决。

//vue axios访问支持跨域   
        protected void Application_BeginRequest(object sender, EventArgs e)
        {
            System.Web.HttpApplication app = sender as System.Web.HttpApplication;
            HttpResponse response = app.Response;
            //支持跨域        
            if (app.Request.HttpMethod == "OPTIONS")
            {
                //支持跨域
                response.AddHeader("Access-Control-Allow-Methods", "*");
                response.AddHeader("Access-Control-Allow-Headers", "*");
                response.AddHeader("Access-Control-Allow-Origin", "*");
                response.AddHeader("Cache-Control", "no-cache");
                response.StatusCode = 200;
                response.End();
            }
            else
            {
                response.AddHeader("Access-Control-Allow-Origin", "*");
                response.AddHeader("Access-Control-Allow-Headers", "*");
                response.AddHeader("Access-Control-Allow-Methods", "*");
                response.AddHeader("Cache-Control", "no-cache");
                response.AddHeader("Access-Control-Allow-Methods", "GET, POST,PUT, DELETE");
                response.AddHeader("Access-Control-Allow-Headers", "Content-Type");
            }
        }