自己回答拉 呵呵
private void button1_MouseEnter(object sender, System.EventArgs e)
{
button1.Size=new System.Drawing.Size(100,60);
}

private void button1_MouseLeave(object sender, System.EventArgs e)
{
button1.Size=new System.Drawing.Size(75,40);
}
MouseEnter是当鼠标进入控件时引发的控件改变，MouseLeave是当鼠标进入控件时引发的控件改变