diff --git a/NewLife.Remoting/IApiHandler.cs b/NewLife.Remoting/IApiHandler.cs
index 341e20d..8566016 100644
--- a/NewLife.Remoting/IApiHandler.cs
+++ b/NewLife.Remoting/IApiHandler.cs
@@ -198,8 +198,9 @@ public virtual ControllerContext Prepare(IApiSession session, String action, Pac
         var pis = method.GetParameters();
         if (pis == null || pis.Length <= 0) return ps;
 
-        // 接口只有一个入参时，客户端可能用基础类型封包传递
-        if (pis.Length == 1 && dic == null && args != null)
+        // 接口只有一个基础类型入参时，客户端可能用基础类型封包传递（字符串）。
+        // 例如接口 Say(String text)，客户端可用 InvokeAsync<Object>("Say", "Hello NewLife!")
+        if (pis.Length == 1 && pis[0].ParameterType.GetTypeCode() != TypeCode.Object && dic.Count == 0 && args != null)
         {
             var pi = pis[0];
             ps[pi.Name] = args.ToStr().ChangeType(pi.ParameterType);
diff --git a/XUnitTest/ApiTest.cs b/XUnitTest/ApiTest.cs
index 70fd209..2c938de 100644
--- a/XUnitTest/ApiTest.cs
+++ b/XUnitTest/ApiTest.cs
@@ -219,4 +219,36 @@ class SPService
 
         public Int64 Test(String key) => _cache.Increment(key, 123);
     }
+
+    [Fact]
+    public async void SimpleType()
+    {
+        using var server = new ApiServer(12377);
+        server.Log = XTrace.Log;
+        server.EncoderLog = XTrace.Log;
+        server.Register<SimpleController>();
+        server.Start();
+
+        using var client = new ApiClient($"tcp://127.0.0.1:{server.Port}");
+
+        var rs = await client.InvokeAsync<String>("Simple/Say", "Hello NewLife!");
+        Assert.Equal("Say: Hello NewLife!", rs);
+
+        var time = DateTime.Now;
+        rs = await client.InvokeAsync<String>("Simple/Login", time);
+        Assert.Equal($"Login: {time.ToFullString()}", rs);
+
+        rs = await client.InvokeAsync<String>("Simple/Login", time.ToFullString());
+        Assert.Equal($"Login: {time.ToFullString()}", rs);
+
+        rs = await client.InvokeAsync<String>("Simple/Login", time.ToString());
+        Assert.Equal($"Login: {time.ToFullString()}", rs);
+    }
+
+    class SimpleController
+    {
+        public String Say(String text) => $"Say: {text}";
+
+        public String Login(DateTime time) => $"Login: {time.ToFullString()}";
+    }
 }
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