Button btn = sender as Button;
System.Drawing.Drawing2D.GraphicsPath btnPath = new System.Drawing.Drawing2D.GraphicsPath();
System.Drawing.Rectangle newRectangle = btn.ClientRectangle;
newRectangle.Inflate(-2, -1);
e.Graphics.DrawEllipse(System.Drawing.Pens.BlanchedAlmond, newRectangle);
newRectangle.Inflate(-2, -4);
btnPath.AddEllipse(newRectangle);
btn.Region = new System.Drawing.Region(btnPath);
以上代码放在按钮的Paint事件中