In power plants and other complex industrial application fields, incomprehensive design can make the system less durable. The fault of the fieldbus, in principle, comes from the physical layer, whose lay-out directly affects the fieldbus’s reliability. This article discusses from four aspects on how to improve the reliability of the physical layer of CAN bus, which include the selection of cables and connectors, the length of the bus and branch lines, the matching method of terminal resistor, and the interface circuit of hardware. Furthermore, the article presents the plan of using H-bridge type matching terminal, which aims at solving signal-reflection problems. Finally, the theory is verified through the application of intelligent electric actuator with the CAN bus.