There are many kinds of grounding protection circuits for urban rail transit in China. Taking the design of Chongqing straddle monorail and power supply system as an example, the design, protection principle and protective coordination relationship of grounding protection device for straddle type monorail car and power supply system were expounded systematically, and the influence of vehicle passing no power area on ground grounding protection design was analyzed and the countermeasures were put forward.