Thank you Mike. Now its working :-)

 Well, there's no tooltip property on the button itself. What you would have to do is apply a tooltip tothe control based on the position of the mouse. You can use UIElements to determine when the mouse is over an editor button. Something like this:

        private void ultraGrid1_MouseEnterElement(object sender, UIElementEventArgs e)
        {
            if (e.Element is EditorButtonUIElement)
            {
                EditorButton button = e.Element.GetContext(typeof(EditorButton)) as EditorButton;
                Debug.WriteLine(button.Key);
                // Set the tooltip here.
            }
        }

        private void ultraGrid1_MouseLeaveElement(object sender, UIElementEventArgs e)
        {
            if (e.Element is EditorButtonUIElement)
            {
                // Clear the tooltip here.
            }
        }   

Thanks for your valuable advise.

Now I am facing another one problem. I want to set ToolTip for those EditorButtons but

I am not getting proper way to do this.  How do I do this?

The reason it does not work is because the button in the grid is not the same button as the one in the combo, it's a clone. 

The easiest thing to do is to trap the EditorButtonClick event of the combo control. Or you could try to get the EditorResolved from a cell and cast it into an EmbeddableEditorButtonBase, get the buttons from there and trap the click event of those buttons. 

Same thing  I am doing. 

I am trapping click event of EditorButtons whatever I added in the Combo.

But they are not firing if I use combo in Grid as a EditorControl.