The Mossbauer spectra for corrosion products formed on A3 ds steel and low alloy 16Mn steel exposed in the Chengdao sea area for 2 years by the electro- connected method were determinal. The phase composition and content of the rust layers on the two steels in four marine corrosion zones were analyzed and studied. Although the phase composition of the two steels were different, their main phase was β-FeOOH. The different content of FEOOH and Fe3O4 in the rust layers illustrated that FeOOH in the inner rist layer participated in the cathodic process as an oxidant accelerating the corrosion rate of steel under wet/ dry cycle condition. Moreover, for the alloy elements in 16Mn steel, the rust layers with simple composition and fine and close texture formed a good barrier layer lowering the corrosion rate of low alloy steel. The Mossbauer spectra for corrosion products formed on A3 ds steel and low alloy 16Mn steel exposed in the Chengdao sea area for 2 years by the electro- connected method were determinal. The phase composition and content of the rust layers on the two steels in four marine The different content of FEOOH and Fe3O4 in the rust layers illustrated that FeOOH in the inner rist layer participated in the cathodic process as an oxidant accelerating the corrosion rate of steel under wet / dry cycle condition. for the alloy elements in 16Mn steel, the rust layers with simple composition and fine and close texture formed a good barrier layer lowering the corrosion rate of low alloy steel .