子窗体在父窗体中打开时为最大化

   Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.IsMdiContainer = True      '设置Form2为MDI窗体
        Me.WindowState = FormWindowState.Maximized
        Dim frm As New Form1          '加载Form1
        frm.MdiParent = Me            '设置Form1为Form2的子窗体
        frm.WindowState = FormWindowState.Maximized        '子窗体最大化
        '当然，你也可以设置子窗体无标题栏等属性
        frm.Show()
    End Sub