Abstract: To ensure the reliability of railway centralized signaling monitoring system (CSM), this paper designed a network topology discovery method based on SNMP, ICMP and port scanning, which could automatically generate the CSM network device topology. This method was implemented through C# language programming to show the network topology generated. Through this method, the physical connection of active node can be found quickly, accurately and comprehensively. It is helpful for the maintenance personnel to monitor the operation state of network equipment remotely, so as to locate, analyze and maintain the equipment fault.