Several methods were used to measure the atmosphere corrosion rusty layer of the carbon steel A₃ and low-alloy steel lOCrMoAl samples from Qingdao. The structure, appearance of steel rusty layer, exisence of alloy elements of steel rest body were disscussed. The main component elements and rust phase of the rusty layer were observed, showing that the relative content of the elements and rust phase varied with the change in corrosion time. The mechanism of the anti-corrosion of the steel was put forward.