Abstract: Starting from the working principle of RS-485 serial port communication in substation, this paper combines a fault solution example that the communication between 16 devices connected to the protocol converter and the centralized control background is interrupted due to the damage of the protocol converter. This paper summarizes the shortcomings of RS-485 bus structure and the search of common faults. Based on the appeal difficulties and the actual situation, it puts forward two solutions: changing the wiring mode through the serial port hub and converting the serial port to Ethernet networking. It can be used for reference to deal with and prevent similar defects on site.