The mobile grounding system of the train realizes the diseharge of electrie energy through the rolling electrical contact between the grounding wheelset and the rail. Since the working grounding wheelset and the protective grounding wheelset share the rail as a discharge channel, the current discharged to the rail through the working grounding is easy to return to the aluminum alloy train body again through the surrounding protective grounding wheelset, so that a circulation current is formed between the train-rail and the long-term train-rail circulating current will lead to electrical corrosion of traction motor bearings and gearbox gears, and raise the potential of the train body, seriously affecting the safety of passengers and equipment on the train. By firstly investigating the related accidents caused by the train-rail circulating current, this paper analyzed the key influencing factors of the train-rail circulation current. Secondly, according to the structure of mobile grounding system, the coupling mechanism of train-rail-catenary grounding return was analysed, and by investigating the simulation model of mobile grounding system, the mechanism of train-rail circulation current and the dynamic change characteristics and distribution law of grounding current were explored. At last the measurements to suppress the train-rail circulating current from three aspects j current, voltage, and impedance and proposed solutions to the problem. Based on current technological means, an online adaptive adjustable resistor was proposed to cope with different grounding conditions. © 2024 Science Press. All rights reserved.