Abstract: Railway safety relays are the key signal products for safe and stable operation of the train. At a certain time, they need to be repaired, replaced, and tested. According to the type of relay, electrical characteristics and contacts, measurement range of coil resistance, etc., it was developed a test system for the railway safety relays. Precise and stable measurement of safety relays was implemented by using INA118 and OPA340 to design the front-end signal processing circuit, using LTC1966 to process the AC signal, using 12 AD converter of STM32 microcontroller to collect analog signal.