@echo off

setlocal

rem DPATH   : 指定目录

rem FILETYPE: 指定文件类型

rem SCONTENT: 替换前的字符串

rem DCONTENT: 替换后的字符串

rem TMPFILE : 临时文件

set DPATH=c:\test

set FILETYPE=*.txt

set SCONTENT=aaa

set DCONTENT=bbb

set TMPFILE=%random%.tmp

for /r %DPATH% %%i in ( %FILETYPE% ) do (

    if exist %TMPFILE% ( del /f/q %TMPFILE% )

    for /f "tokens=*" %%j in ('type "%%i"')

      set TMP=%%j

      echo !TMP:%SCONTENT%=%DCONTENT%!>nul 1>>%TMPFILE%

    )

    move /y %TMPFILE%  %%i

)

endlocal