Abstract: The effect of Cr and Mo content on corrosion resistance and mechanical properties of weathering steel deposited metal was investigated by cycle immersion corrosion test, rust layer micro-analysis and electrochemical test. The experimental results indicate that corrosion resistance of deposited metal was improved with the increase of Cr and Mo contents. Mo improved I he corrosion resistance better than Cr. Cr and Mo enriched in the rust layer as Cr₂O₃, FexCr_3-xO₄,MnFexCr_2-xO₄, Mn_1-xFex-Cr₂0₄, NiFe_xCr_2-x0₄ and MoO₃,which promoted the compactness of rust layer, impeded the anode dissolution and enhanced the protecting performance of rust,so the corrosion resistance of deposited metal was improved. With the increase of Cr and Mo contents, the strength of deposited metal also improved, whereas the impact toughness declined sharply. At the same time, the contents of M-A constituent and granular bainite increased while the acicular ferrite decreased. The change of microstructure was the main reason for increase of strength and deterioration of toughness.