以下是代码做你想要什么：

Following is the code to do what you want:

假设Button1的是在父窗体

Assume that button1 is in the parent form.

private void button1_Click(object sender, EventArgs e)
        {
            this.IsMdiContainer = true;
            Form Form2 = new Form();
            Form2.MdiParent = this;
            Form2.Show();
        }

还有以下链接将为您提供更多更好的，你想做什么细节

Also the following link will provide you more better details of what you want to do:

HTTP：// WWW .codeproject.com / KB / CS / mdiformstutorial.aspx

希望这有助于...