vb 怎么回事

Dim arr(), stt() As String 将这句 改成Dim arr() As String, stt(2) As String
另外注意"," 逗号的全半角，如果 a = "301,289,我" 里面的逗号和arr = Split(a, ",") 里面的逗号不一样的话，也会出错

帮你改了下
Private Sub Command1_Click()
Dim a As String
Dim arr() As String, stt(1) As String
Dim fhz As Double
Dim jj As Integer
a = "301,289,我"
arr() = Split(a, ",")
For jj = LBound(arr) To UBound(arr) - 1
stt(jj) = Mid(arr(jj), 1, 1)
Next
MsgBox stt(0)
MsgBox stt(1)
End Sub

Private Sub Command1_Click()

Dim a As String
Dim arr
Dim stt(3) As String
Dim fhz As Long
Dim jj As Integer

a = "301,289,我"
arr = Split(a, ",")
fhz = UBound(arr)

For jj = 0 To fhz - 1

stt(0) = Mid(arr(jj), 1, 1)
stt(1) = Mid(arr(jj), 2, 1)
stt(2) = Mid(arr(jj), 3, 1)
MsgBox st