Objective To study the corrosion behavior and corrosion mechanism of 16Mn steel in alkaline solution containing 4 g/ L Na2S2O3. Methods The corrosion morphology of 16Mn steel was observed, the components of the corrosion products were analyzed by EDS, and the variation in corrosion rate was analyzed using the mass loss method and dynamic method to determine the corrosion mechanism. Results With the increase of corrosion time, the corrosion morphology evolved from the initial pitting corrosion to uniform corrosion, and the corrosion products mainly consisted of O, S, Na, Fe elements. Conclusion The corrosion products were mainly amorphous and crystalline FeOOH and Fe3O4. With the extension of corrosion time, the corrosion became more and more serious, and the corrosion rate gradually decreased.