Hi deng yingxin,
You are right, there is a bug in RadRichTextBox that causes appearing of both parent and self context menus. This should be fixed in the next version (2011 Q2). As a temporary workaround, you could close the parent menu just after opening the RadRichTextBox context menu:
.radRichTextBox1.ContextMenu).Opened += (s, a) =>
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All the best,
the Telerik team
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