RT，尝试过在PICTUREBOX中实现同样的功能，但是也是一样会闪。
为什么在透明窗体中画线就会闪？有没有解决办法？
先谢谢各位啦！
下面附上代码（测试如下代码，需要添加Timer控件）：

Option Explicit

Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hWnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long

Private Const WS_EX_LAYERED = &H80000
Private Const GWL_EXSTYLE = (-20)
Private Const LWA_ALPHA = &H2
Private Const LWA_COLORKEY = &H1

Dim i As Integer

Private Sub Form_Load()
    Dim rtn As Long
    Me.BackColor = vbBlue
    Me.BorderStyle = 0
    rtn = GetWindowLong(hWnd, GWL_EXSTYLE)
    rtn = rtn Or WS_EX_LAYERED
    SetWindowLong hWnd, GWL_EXSTYLE, rtn
    SetLayeredWindowAttributes hWnd, vbBlue, 100, LWA_COLORKEY
    Timer1.Interval = 800
    Timer1.Enabled = True
End Sub

Private Sub Timer1_Timer()
    i = i + 100
    Me.Cls
    Me.DrawWidth = 2
    Me.Line (0, 0)-(800, i), vbRed
    Me.DrawWidth = 9
    Me.PSet (300, 300), vbGreen
End Sub

Private Sub Timer1_Timer()
    i = i + 100
'    Me.Cls
    Me.DrawWidth = 2
    Me.Line (0, 0)-(800, i), vbblue, bf
    Me.Line (0, 0)-(800, i), vbRed
    Me.DrawWidth = 9
    Me.PSet (300, 300), vbGreen
End Sub

thank you 版主