Abstract: A Mo series rust layer stabilizer was prepared on the surface of weathering steel. The effects of the rust layer stabilizer on the structure, composition and corrosion resistance of the rust layer of weathering steel were studied by alternate-immersion corrosion test, macroscopic and microscopic corrosion morphology observation, rust layer composition analysis and electrochemical test. The results showed that the rust layer stabilizer could avoid the phenomenon of rust liquid flow, reduce the corrosion rate of weathering steel, promote the accumulation of Mo element at the junction between inner rust layer and matrix, promote the formation of α-FeOOH, generate stable oxide MoO₃ and insoluble FeMoO₄, increase the resistance of rust layer, and improve the corrosion resistance of weathering steel.