diff --git a/src/component/tooltip.js b/src/component/tooltip.js
index f405bc49488d82d33ebe193ff1bbdcb9221586e4..76cd761df8dc6c8cae142917d4fa68045a3bb88e 100644
--- a/src/component/tooltip.js
+++ b/src/component/tooltip.js
@@ -72,6 +72,7 @@ define(function (require) {
         this._tDom.onmouseout = function() {
             self._mousein = false;
         };
+        this._tDom.className = 'echarts-tooltip';
         this._tDom.style.position = 'absolute';  // 不是多余的，别删！
         this.hasAppend = false;