The work aims to change the structure of heavy rail steel by adding Cr to it, and study the resistance of the structure to atmospheric corrosion. U71Mn was smelted in an intermediate frequency induction furnace and then air cooled after rolled. The pearlite layer spacing of the experimental steel was measured by SEM. The corrosion of the experimental steel in the industrial atmosphere was simulated in NaHSO3 solution with a concentration of (1.0±0.05)×10-2 mol/L. The weight loss rate, SEM, XRD and Electrochemical methods were used to study the resistance of pearlite structure to atmospheric corrosion. The average corrosion rate increased firstly and then decreased with the increase of corrosion time and finally tended to be steady. The corrosion rate was the fastest at 120 h, and the rust layer with a certain protective effect formed at 240 h had the slowest corrosion rate. After 360 h, the corrosion resistance tended to be gentle. When the sheet spacing of U71Mn pearlite structure of heavy rail steel was 0.2910 μm, 0.2500 μm and 0.2238 μm, the corrosion loss of the experimental steel gradually increased, and the average corrosion weight loss rate was 1.572 g/(m2?h), 1.387 g/(m2?h) and 1.190 g/(m2?h), the ratio of α/γ* in the rust layer increased by 0.717, 0.868, and 0.997, respectively, and the polarization resistance increased by 3.715 Ω?cm2, 8.604 Ω?cm2 and 13.739 Ω?cm2, and the equivalent capacitance of the rust layer was sequentially decreased to 8.434′10-6 F/cm2, 0.411′ 10-6 F/cm2 and 0.081′10-6 F/cm2, respectively. Therefore, as the spacing of the pearlite sheets and the corrosion weight loss rate become smaller, the ratio of the rust layer α/γ* and the polarization resistance become larger and the corrosion rate slows down, which leads to smaller pores and thickness of the rust layer as well as finer gap, thus achieving good bonding ability between rust layer and substrate and improving the resistance to atmospheric corrosion.