Abstract: The abnormal corrosion of stray current materials in DC traction power supply system under the condition of metro multi line crossing is studied. Firstly, the stray current model of single line under tunnel condition is established, and the influence of train power supply mode, operation mode, soil resistivity and insulation design on stray current is studied. The results show that the stray current generated in the power supply section under the condition of single side feeding is significantly higher than that under the condition of two sides feeding. Larger stray current will be generated when the train accelerates and regenerative braking. The magnitude of stray current decreases with the increase of soil resistivity and rail ground transition resistance in the operation section. Secondly, the stray single flow model of cross line under tunnel condition is established to study the potential distribution and electric field distribution of soil in the middle of cross line tunnel. The results show that the electric potential and electric field in the soil between tunnels are too large, and corresponding measures should be taken to prevent stray current corrosion of metal pipelines. Combined with the characteristics of new concrete, the influence of concrete ballast with fly ash and other admixtures on stray current is studied. The results show that the stray current of the DC traction power supply system decreases with the decrease of the conductivity of the doped concrete, which provides the basis for the stray current suppression method of the DC traction power supply system of metro.