Abstract: The corrosion resistance of S355J2W weathering steel in solution of NaHSO3 was studied compared with Q345R low-alloy steel by means of the periodical immersed corrosion test, and the corrosion production was observed by scanning electron microscopy. The results show that under the same testing conditions, the average corrosion rate of S355J2W weathering steel was lower than that of Q345R low-alloy steel. Black-brown fine rust layer was formed on the surface of S355J2W weathering steel, while the surface of Q345R low-alloy steel was covered by orange loose rust layer. The morphology of corrosion products of S355J2W weathering steel grew along the direction of radioactive acicular crystal, and Q345R low-alloy steel corrosion products were the accumulation of granular polymers without shape rules, and there were big gaps between the particles.