With ARM processor as upper computer and MCU as lower computers, a monitoring and controlling system for combine harvester is constructed in this paper. CAN bus is used here to realize decentralized control and centralized management. By monitoring and controlling running status of lower computers and relevant parameters through upper computer, the unit can work under an optimum working condition. Therefore, the unit’s work efficiency will be increased, and the fault rate will be reduced. Experiment shows that, upper computer can communicate with lower computers reliably. The expected goal is realized.