Dim ar() As Byte
Open "C:\Users\bocheng\Desktop\1.txt" For Binary As #1
ReDim ar(1 To LOF(1)) As Byte
    Get #1, , ar
Close #1
Open "C:\Users\bocheng\Desktop\2.txt" For Binary As #1
    Put #1, , ar
Close #1

2.txt比1.txt后面多个空格

Dim ar() As Byte
Open "C:\Users\bocheng\Desktop\1.txt" For Binary As #1
ReDim ar(1 To LOF(1)) As Byte
    Get #1, , ar
Close #1
Open "C:\Users\bocheng\Desktop\2.txt" For Binary As #1
    Put #1, , ar
Close #1

Open "C:\Users\bocheng\Desktop\2.txt" For Binary As #1
    Get #1, , ar
Close #1
Open "C:\Users\bocheng\Desktop\3.txt" For Binary As #1
    Put #1, , ar
Close #1
End

2.txt还是多个空格，3.txt就正常，谁来解释下？

我改在E盘操作，测试代码生成的结果没问题。

E:\>fc 1.txt 2.txt  /b
正在比较文件 1.txt 和 2.TXT
FC: 找不到差异

E:\>fc 3.txt 2.txt /b
正在比较文件 3.txt 和 2.TXT
FC: 找不到差异

所以搞不懂你的问题出在哪里了。
文件内包含中文也是如此。