如题，若能改，告之改法，谢谢

说错了，是改为圆的按钮

新建个类比如RoundButton.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Windows.Forms;

namespace WindowsFormsApplication2
{
    public class RoundButton : System.Windows.Forms.Button
    {
        public RoundButton() 
        {
            Rectangle rec = this.ClientRectangle;
            rec.Size = new Size(50,50);
            rec.X += 3;
            rec.Y += 3;
            
            using (GraphicsPath p = new GraphicsPath())
            {
                p.AddPie(rec,0f,360f);
                this.Region = new Region(p);
            }
        }
    }
}

把按钮从工具栏中拽过去，然后改下这个就能看到效果了。

        private void InitializeComponent()
        {
            this.roundButton1 = new WindowsFormsApplication2.RoundButton();
            this.SuspendLayout();

            this.roundButton1.BackColor = System.Drawing.Color.Red;
            this.roundButton1.Location = new System.Drawing.Point(34, 21);
            this.roundButton1.Name = "roundButton1";
            this.roundButton1.Size = new System.Drawing.Size(57, 57);
            this.roundButton1.TabIndex = 0;
            this.roundButton1.UseVisualStyleBackColor = false;

            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.None;
            this.BackgroundImageLayout = System.Windows.Forms.ImageLayout.None;
            this.ClientSize = new System.Drawing.Size(292, 266);
            this.Controls.Add(this.roundButton1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

说明下，RoundButton 继承 Button 写完类后会自动添加到工具栏窗体最上面，以后用就直接拽吧。我临时写的按钮大小固定死了，要用可以自己改改 rec.Size 改成从参数读吧。

好办法，谢谢帮助