Control Area Network(CAN) bus is widely used in industry control and industry automation. A high-credibility supervision unit is successfully developed based on CAN bus. First, characteristics, feasibility and advantages of CAN bus in modules with high credibility are analyzed. Then, software and hardware of high-credibility supervision unit are designed based on Advanced RISC Machines(ARM) Single Chip Microcomputer(SCM) and CAN bus, and the state control and test to high-credibility module is realized. Experiment results indicate that the proposed unit achieves real time capability and reliability, and its supervision mission to high-credibility module is well accomplished.