Abstract: A rust layer stabilizer for weathering steel was prepared by using chromium sulfate as accelerator and polyvinyl butyral ester as film forming agent. The effects of the stabilizer on the structure, composition and corrosion resistance of rust layer on surface of weathering steel were studied by cyclic immersion corrosion test and electrochemical test. The results showed that the rust layer stabilizer could avoid the phenomenon of rust liquid hanging, reduced the corrosion rate of weathering steel, promoted the aggregation of Cr element at the joint of inner rust layer and matrix, refined the grains of rust layer, increased the resistance of rust layer and improved the corrosion resistance of weathering steel.