修改一下主楼的代码（转录错误，根据网上原稿改正，原稿是不让复制的）：
蝶形算法代码
Sub 蝶形算法(xr() As Double)
 Dim l As Long, le As Long, le1 As Long, n As Long, r As Long, p As Long, q As Long, m As Byte
 Dim wr As Double, w1 As Double, wlr As Double, wl1 As Double, tr As Double, t1 As Double
 Dim pi As Double, t As Double
 Dim xi()
 n = UBound(xr) '求数组大小，其值必须是2的幂
m = 0
 l = 2
 pi = 3.14159265358979
 Do
  l = l + l
  m = m + 1
  Loop Until l > n
  n = l / 2
 ReDim xi(n - 1)

 l = 1
 Do
   le = 2 ^ l
   le1 = le / 2
   wr = 1
   wi = 0
t=pi/le1 '这一步缺少t值，补上了
   w1r = Cos(t)
   w1i = -Sin(t)
   r = 0
 Do
   p = r
   Do
    q = p + le1
   
    tr = xr(q) * wr - xi(q) * wi
    ti = xr(q) * wi + xi(q) * wr
   
    xr(q) = xr(p) - tr
    xi(q) = xi(p) - ti
    xr(p) = xr(p) + tr
    xi(p) = xi(p) + ti
   
    p = p + le
 Loop Until p > n - 1

 wr = wr * w1r - wi * w1i
 wi = wr * w1i + wi * w1r '这一步用+法
 r = r + 1
 Loop Until r > le1 - 1
 l = l + 1
 Loop Until l > m

 For i = 0 To n - 1 '仅输出模
   xr(i) = Sqr(xr(i) ^ 2 + xi(i) ^ 2)
    Next
   
 End Sub

修改以后运行结果仍然不对，咋回事呢？

上班呢，明白了点好像，输入的时候各位数字要倒序：序号为01234567时，倒序为04261537
原数为00000678倒序为：
00070608.
下班试试吧

Private Sub Command1_Click()
Dim xr() As Double, a As String
a = Trim(Text1)
ReDim xr(0 To Len(a) - 1)
For i1 = 0 To Len(a) - 1
xr(i1) = Mid(a, i1 + 1, 1)
  Next
Dim l As Long, le As Long, le1 As Long, n As Long, r As Long, p As Long, q As Long, m As Byte
Dim wr As Double, w1 As Double, wlr As Double, wl1 As Double, tr As Double, t1 As Double
Dim pi As Double, t As Double
Dim xi()
n = Len(a) '求数组大小，其值必须是2的幂
m = 0
l = 2
pi = 3.14159265358979
Do
 l = l + l
 m = m + 1
 Loop Until l > n
 n = l / 2
ReDim xi(n - 1)

l = 1
Do
  le = 2 ^ l
  le1 = le / 2
  wr = 1
  wi = 0
  If l = 1 Then
  t = 0
  Else
  t = pi / le1
  End If
  w1r = Cos(t)
  w1i = -Sin(t)
  Print l
  r = 0
Do
  p = r
  Do
   q = p + le1
   
   tr = xr(q) * wr - xi(q) * wi
   ti = xr(q) * wi + xi(q) * wr
   
   xr(q) = xr(p) - tr
   xi(q) = xi(p) - ti
   xr(p) = xr(p) + tr
   xi(p) = xi(p) + ti
   Print p, q
   
   Print xr(p), xr(q)
   
   
   p = p + le
Loop Until p > n - 2

wr = wr * w1r - wi * w1i
wi = wr * w1i + wi * w1r
r = r + 1
Loop Until r > le1 - 1
l = l + 1
Loop Until l > m

For i = 0 To n - 1 '仅输出模
   xr(i) = Sqr(xr(i) ^ 2 + xi(i) ^ 2)
   Text2 = Text2 & "  " & xr(i) & "+" & xi(i) & "i"
   Next

End Sub

Private Sub Command2_Click()
Text1 = ""
Text2 = ""
End Sub

 输入：Text1 =80607000，结果：
    21+0i  13.4143937430245+-3.50000000000001i  4.40338197130883+-3.19974746830584i  6.56830852046515+-1.17525253169417i  
7+0i  4.64263292831844+3.49999999999999i  3.3449607857897+3.19974746830584i  9.60982505463419+1.17525253169419i
与正确值比较：12.9+10.9i, 2+7i, 3.1-1.1i, 7, 3.1+1.1i, 2-7i, 12.9-10.9i, 21也是不对。

例第A0项为：8→14→21最终输出21.
实际为8+6+7=21.
而第A1项为：8→8.0000000001→12.9492……最终输出13.41439……，咋回事呢？
实际为：8+7*0.7+6*0=8+4.9=12.9.
发一下截图：

速度快，可惜输出结果不对，不知道怎么改。

Private Sub Command1_Click()
Dim xr() As Double, a As String
a = Trim(Text1)
ReDim xr(0 To Len(a) - 1)
For i1 = 0 To Len(a) - 1
xr(i1) = Mid(a, i1 + 1, 1)
  Next
Dim l As Long, le As Long, le1 As Long, n As Long, r As Long, p As Long, q As Long, m As Byte
Dim wr As Double, w1 As Double, wlr As Double, wl1 As Double, tr As Double, t1 As Double
Dim pi As Double, t As Double
Dim xi()
n = Len(a) '求数组大小，其值必须是2的幂
m = 0
l = 2
pi = 3.14159265358979
Do
 l = l + l
 m = m + 1
 Loop Until l > n
 n = l / 2
ReDim xi(n - 1)

l = 1
Do
  le = 2 ^ l
  le1 = le / 2
  wr = 1
  wi = 0
  t = pi / le1
  w1r = -Cos(t)
  w1i = Sin(t)
  r = 0
Do
  p = r
  Do
   q = p + le1
   
   tr = xr(q) * wr - xi(q) * wi
   ti = xr(q) * wi + xi(q) * wr
   
   xr(q) = xr(p) - tr
   xi(q) = xi(p) - ti
   xr(p) = xr(p) + tr
   xi(p) = xi(p) + ti
   p = p + le
Loop Until p > n - 1

wr = wr * w1r - wi * w1i
wi = wr * w1i + wi * w1r
r = r + 1
Loop Until r > le1 - 1
l = l + 1
Loop Until l > m

For i = 0 To n - 1 '仅输出模
   
   Text2 = Text2 & "  " & xr(i) & "+" & xi(i) & "i"
   Next
End Sub

Private Sub Command2_Click()
Text1 = ""
Text2 = ""
End Sub

输入：Text1 =80607000，结果：
 21+0i  3.05025253169415+-3.50000000000001i  7.97487373415292+6.69974746830583i  -0.962310601229371+-11.0747474683058i
  7+0i  12.9497474683058+3.49999999999999i  -3.97487373415292+-6.69974746830583i  16.9623106012294+11.0747474683058i
与正确值比较：12.9+10.9i, 2+7i, 3.1-1.1i, 7, 3.1+1.1i, 2-7i, 12.9-10.9i, 21也是不对。

可能是内层循环程序的乘法顺序不对了，不太懂原理，无法修改，望老师指正！

Private Sub Command1_Click()
Dim xr() As Double, a As String
a = Trim(Text1)
ReDim xr(0 To Len(a) - 1)
For i1 = 0 To Len(a) - 1
xr(i1) = Mid(a, i1 + 1, 1)
  Next
Dim l As Long, le As Long, le1 As Long, n As Long, r As Long, p As Long, q As Long, m As Byte
Dim wr As Double, w1 As Double, wlr As Double, wl1 As Double, tr As Double, t1 As Double
Dim pi As Double, t As Double
Dim xi()
n = Len(a) '求数组大小，其值必须是2的幂
m = 0
l = 2
pi = 3.14159265358979
Do
 l = l + l
 m = m + 1
 Loop Until l > n
 n = l / 2
ReDim xi(n - 1)

l = 1
Do
  le = 2 ^ l
  le1 = le / 2
  wr = 1
  wi = 0
  t = pi / le1
  w1r = Cos(t)
  w1i = -Sin(t)
  r = 0
Do
  p = r
  Do
   q = p + le1
   
   tr = xr(q) * wr - xi(q) * wi
   ti = xr(q) * wi + xi(q) * wr
   
   xr(q) = xr(p) - tr
   xi(q) = xi(p) - ti
   xr(p) = xr(p) + tr
   xi(p) = xi(p) + ti
   p = p + le
Loop Until p > n - 1

wr = wr * w1r - wi * w1i
wi = wr * w1i + wi * w1r
r = r + 1
Loop Until r > le1 - 1
l = l + 1
Loop Until l > m

For i = 0 To n - 1 '仅输出模
   
   Text2 = Text2 & "  " & xr(i) & "+" & xi(i) & "i"
   Next
End Sub

Private Sub Command2_Click()
Text1 = ""
Text2 = ""
End Sub

 输入：Text1 =80607000，结果：
 21+0i  12.9497474683058+-3.50000000000001i  3.02512626584709+-3.19974746830584i  6.46231060122937+-1.17525253169417i  
7+0i  3.05025253169417+3.49999999999999i  0.974873734152908+3.19974746830584i  9.53768939877061+1.17525253169419i
与正确值比较：12.9+10.9i, 2+7i, 3.1-1.1i, 7, 3.1+1.1i, 2-7i, 12.9-10.9i, 21也是不对。

Private Sub Command1_Click()
Dim xr() As Double, a As String
a = Trim(Text1)
b = Trim(Text3)
ReDim xr(0 To Len(a) - 1): ReDim yr(0 To Len(b) - 1): ReDim zr(0 To Len(b) - 1)
For i1 = 0 To Len(a) - 1
xr(i1) = Mid(a, i1 + 1, 1)
yr(i1) = Mid(b, i1 + 1, 1)

  Next
Dim l As Long, le As Long, le1 As Long, n As Long, r As Long, p As Long, q As Long, m As Byte
Dim wr As Double, w1 As Double, wlr As Double, wl1 As Double, tr As Double, t1 As Double
Dim pi As Double, t As Double, tr1 As Double
Dim xi(): Dim yi(): Dim zi()
n = Len(a) '求数组大小，其值必须是2的幂
m = 0
l = 2
pi = 3.14159265358979
Do
 l = l + l
 m = m + 1
 Loop Until l > n
 n = l / 2
ReDim xi(n - 1): ReDim yi(n - 1): ReDim zi(n - 1)

l = 1
Do
  le = 2 ^ l
  le1 = le / 2
  wr = 1
  wi = 0
  t = pi / le1
  w1r = Cos(t)
  w1i = -Sin(t)
  r = 0
Do
  p = r
  Do
   q = p + le1
   
   tr = xr(q) * wr - xi(q) * wi
   ti = xr(q) * wi + xi(q) * wr
   
   tr1 = yr(q) * wr - yi(q) * wi
   ti1 = yr(q) * wi + yi(q) * wr
   
   xr(q) = xr(p) - tr
   xi(q) = xi(p) - ti
   xr(p) = xr(p) + tr
   xi(p) = xi(p) + ti
   
    yr(q) = yr(p) - tr1
   yi(q) = yi(p) - ti1
   yr(p) = yr(p) + tr1
   yi(p) = yi(p) + ti1
   
   p = p + le
Loop Until p > n - 1

wr = wr * w1r - wi * w1i
wi = wr * w1i + wi * w1r
r = r + 1
Loop Until r > le1 - 1
l = l + 1
Loop Until l > m

For i = 0 To n - 1 '仅输出模
   zr(i) = xr(i) * yr(i) - xi(i) * yi(i): zi(i) = xr(i) * yi(i) + xi(i) * yr(i)
   Text2 = Text2 & "  " & zr(i) & "+" & zi(i) & "i"
   Next
End Sub

Private Sub Command2_Click()
Text1 = ""
Text2 = ""
Text3 = ""
End Sub


 输入：Text1 =80607000，Text2=20403000,结果：
 189+0i  48.1200576850889+-33.8492424049177i  -9.10907287525383+0.845301243345486i  8.07394476689+-4.83093657874164i
  21+0i  -5.62005768508875+4.15075759508251i  -6.76592712474619+-6.46840725563929i  24.7688582392567+7.92894805108087i
这个与正确值不同，不知道逆变换能不能出来正确结果？

正确结果是：将她们逐项相乘得到向量 {Ck}，即 { C7, C6, C5, C4, C3, C2, C1, C0 }
= { -13.6+123.4i, -25-8i, -2.4-5.8i, 21, -2.4+5.8i, -25+8i, -13.6-123.4i, 189 }