Form form = new Form();
            Point p = new Point(1000,390);
            form.StartPosition = FormStartPosition.Manual;
            form.Location = p;
            form.Show();

------解决方案--------------------
C# code

        private void btnEdit_Click(object sender, EventArgs e)
        {
            Form2 frm = new Form2();
            frm.X = this.Left + ((Button)sender).Left;
            frm.Y = this.Top +((Button)sender).Bottom;
            frm.ShowDialog(this);
        }