Abstract: Taking MPC5744 P as an example, the low-level driver of Controller Area Network Calibration Protocol（CCP） was developed for online calibration measurement of heavy tractor controller.According to CCP’s requirement, FlexCAN module, PIT module and Flash module’s underlying driver are developed.In order to calibrate the program online, a corresponding upper computer is designed by using Python external tool PyQt5.In order to verify the performance of the designed system, MPC5744 P microcontroller was used to calibrate and measure the variables online.The experimental results show that the designed CCP can accurately achieve the online calibration and measurement of variables through the interaction with the upper computer, which meets the design requirements.