Abstract: Based on the urban rail transit conventional running rail return system, the characteristics of special rail return system are analyzed. Targeting catenary+return rail traction power supply system and power supply rail+return rail traction power supply system, the working principle of DC ground electricity leakage protection device is elaborated. In the catenary+return rail traction power supply system DC ground protection scheme, the ground electricity leakage protection device is set up between substation DC negative pole and ground, it is capable to perform selective positive pole is capable of selective protection of various short-circuit faults in the DC system like positive to negative, positiue to overhead ground wire, positive to steel rail and vehicle shell. The power supply rail+return rail traction power supply system adopts 64D ground electricity leakage protection device, through a series of improvement, it can be cut off the fault circuit to realize selective protection.