Abstract: It is difficult for automobile calibration system software to be universally applicable to different application scenarios. According to the national standard，a kind of steering wheel angle calibration and diagnosis software based on CAN protocol for power steering system was designed. The initial parameters were determined according to the communication protocol type，and the data communication connection between the diagnostic instrument and the automobile ECU was established. Then，the data of ECU was sampled and analyzed，and the calibration simulation database was obtained. Finally，the program was designed to realize the calibration function of the diagnosis instrument. The test operation shows that the software can achieve the expected calibration function and can reduce the complexity of the calibration work.

Key words: automobile power steering system, calibration, fault diagnosis, CAN protocol