With the widespread use of subway, the impact of subway on the surrounding equipment is becoming more and more serious, but in addition to the subway stray current, the induction current generated in the power system by the space time-varying magnetic field caused by the train operation is also one of the important factors threatening the safety of power transformers, and it is urgent to explore the characteristics of the influence of the subway magnetically induced current on power transformers and the influencing factors of the induced current. In this paper, we construct a simulation model of electromagnetic coupling between the traction power supply system of subway and the equivalent closed circuit of power system, verify the correctness of the simulation model by combining the time- frequency characteristics of the measured transformer neutral current, and use the model to analyze the influencing factors affecting the magnetically induced voltage.