我已经解决
form1中
Private Sub FlatButton1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles FlatButton1.Click
Dim kk As Form2
kk = New Form2(Me)
kk.Show()
End Sub
form2中
Public kkk As Form1
Public Sub New(ByRef kk As Form)
MyBase.New()
kkk = kk
'该调用是 Windows 窗体设计器所必需的。
InitializeComponent()
'在 InitializeComponent() 调用之后添加任何初始化
End Sub
Private Sub Form3_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
If IsNothing(kkk) = False Then
CType(kkk, Form1).FlatButton1.Width = 10
End If
End Sub