diff --git a/src/widget/datetime/datetime.combo.js b/src/widget/datetime/datetime.combo.js
index d436da1a8..28037bb69 100644
--- a/src/widget/datetime/datetime.combo.js
+++ b/src/widget/datetime/datetime.combo.js
@@ -9,9 +9,9 @@ BI.DateTimeCombo = BI.inherit(BI.Single, {
         border: 1,
         iconWidth: 24
     },
-    _defaultConfig: function () {
+    _defaultConfig: function (conf) {
         return BI.extend(BI.DateTimeCombo.superclass._defaultConfig.apply(this, arguments), {
-            baseCls: "bi-date-time-combo bi-border bi-border-radius",
+            baseCls: "bi-date-time-combo bi-focus-shadow " + (conf.simple ? "bi-border-bottom" : "bi-border bi-border-radius"),
             width: 200,
             height: 24,
             minDate: "1900-01-01",