Stray currents can erode buried metal pipes and reinforced concrete structures along the subway to reduce the strength and durability of the building. The existing stray current distribution model is mostly driven by a single train and the boundary conditions are one or two substations. There are defects such as simple model structure and large difference between boundary conditions and actual conditions, As a result, there is a large error between the simulation results and the measured values. Firstly, the train and the substation are equivalent to the DC source to inject current into the ground, and then based on the distribution characteristics of the stray current, based on the actual situation, the "traveling track - drainage steel structure - metal mesh - earth soil" four The layer-to-earth network structure method uses the micro-equivalent circuit to derive the distribution model of the earth"s electric quantity under the action of a single injection source, and then superimposes the results of the individual injection sources to obtain the distribution model of the electric quantity on the whole line. Finally, based on the data of Chengdu subway line, the stray current distribution model of the multi-train is used to program and simulate the stray current of the whole line, and predict its distribution on the whole line. Provide reference for pre-construction and post-protection of subway stray current.