A leak current detection module for a train power supply monitoring subsystem comprises a power circuit, a communication circuit, a CPU control circuit and a signal measurement circuit. The power circuit provides a required power supply for the communication circuit, the CPU control circuit and the signal measurement circuit. The CPU control circuit is in communication with a DC600V power supply device, an upper computer and a 6A system through the signal measurement circuit and the communication circuit. By means of the leak current detection module for the train power supply monitoring subsystem, the leak current numerical value of the DC600V power supply device can be detected, a task can be sent, and therefore electric leakage information of the power supply device can be obtained in real time; the collected information is uploaded, safety information such as grounding leakage current of the power supply device is displayed on a 6A display interface of a driver control cabinet, and therefore the state of the power supply device can be judged in advance, the faults which can be possibly generated can be prevented in advance, and the aim of safely supplying power to a train is achieved.