怎么把文字的文本框变成圆的

不能，只能改变字体，不能改变文本框的形状

Private Declare Function CreateEllipticRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long
Private Declare Function SetWindowRgn Lib "user32" (ByVal hWnd As Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long

Private Sub Form_Load()
Show
Me.ScaleMode = 3
rgn = CreateEllipticRgn(0, 0, Text1.Width, Text1.Height)
SetWindowRgn Text1.hWnd, rgn, 1
End Sub

没办法直接变成圆的。但是可以通过贴背景图形成圆的效果——当然只是一种假象。