Abstract: The periodic immersion corrosion experiment was adopted to simulate the acidic marine atmosphere environment. The corrosion behavior and corrosion resistance mechanism of Mo-containing low alloy steels were analyzed by weight loss experiment, electrochemical experiment, scanning electron microscopy, energy disperse spectroscopy and X-ray diffraction spectroscopy. The results showed that the microstructures of low alloy steels with Mo mass fraction of 0.2%, 0.4%, 0.6%, 0.8% and 1.0% were composed of ferrite and pearlite. In the early stage of corrosion, the corrosion products of low alloy steels did not show obvious delamination when Mo content was 0.2%~0.8%, and all samples showed obvious delamination in the middle and late corrosion periods. The rust layer became thicker with the increase of immersion time, and when Mo content was 0.4%, the inner rust layer could provide better protection with relatively denser layer and smaller cracks to the substrate. The corrosion rates of the 5 low alloy steels increased first and then decreased with the increase of immersion time. When Mo content was between 0.2% to 0.4%, it could improve the corrosion resistance performance, while when Mo content was beween 0.6% to 1.0%, it had a small influence on enhancing the corrosion resistance, which was consistent with the results of rust layer analysis and weight loss test.