出现该问题的原因是在默认的Golbal.asax.cs文件中已经注册了默认路由

public class MvcApplication : System.Web.HttpApplication
    {
        public static void RegisterRoutes(RouteCollection routes)
        {
            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

//routes.MapRoute(
            //    "Default", // 路由名称
            //    "{controller}/{action}/{id}", // 带有参数的 URL
            //    new { controller = "Home", action = "Index", id = UrlParameter.Optional } // 参数默认值
            //);

routes.MapRoute(
                  "Member",
                  "Member/{action}/{page}",
                  new { controller = "MemberCenter", action = "List" },
                  new { action = @"Index|List|Detail", page = @"\d+" }
                );

routes.MapRoute(
                  "Default",
                  "{controller}/{action}/{id}",
                  new { controller = "Home", action = "Index", id = UrlParameter.Optional },
                  new string[] { "MvcStudyDemo.Controllers" }
                  );

}

而在AREAS中有注册了一个同名的Controller

public override void RegisterArea(AreaRegistrationContext context)
        {
            context.MapRoute(
                "Order_default",
                "Order/{controller}/{action}/{id}",
                new { action = "Index", id = UrlParameter.Optional },
                new string[] { "MvcStudyDemo.Areas.Order.Controllers" }
               
            );
        }

解决方法就是在每个注册Router的时候加上命名空间即可。