Abstract Taking the railway network of a certain region as an example, this paper introduces the traction law of the metro in urban rail transit and the common power supply mode between traction stations. The finite element modelling of vehicle operating conditions was carried out using simulation software to analyze the interference law of stray currents of city rail on soil potential and rail potential at different times under unilateral and bilateral power supply modes. The results show that the influence of different working conditions is different, and the two-sided power supply mode can restrain the influence of stray current compared with the single-sided power supply mode.