Abstract: The paper introduced topology and working principle of each module of intelligent 3.3 kV mine-used combined switchgears control system. For demands of reliability and real-time performance of communication of the control system, it proposed a design scheme of communication system for mine-used combined switchgears based on master-slave structure by use of microcontroller C8051F040 and RS485 bus, and introduced hardware design, communication protocol and implementation process of communication between upper computer and lower computer in details. The testing results showed the communication system is correct and reliable in data transmission with high real-time performance.