Abstract: In view of problem of wasting time and energy and low efficiency in calibrating process of existing calibration method of strain gauges which adopts single-channel manual operation mode, an auto-calibration system based on cortex-M3 MCU was designed，hardware and software design of the system were introduced in details. The system can output standard resistance signal to input terminal of calibration bridge , and can automatically compute precision of calibrate bridge through comparison value between actual outputs and theoretical outputs. The experimental results show that the system can perform auto-calibration of strain gauge efficiently with calibration precision at 0.5%.