Abstract: The effects of Cr on the mechanical properties and corrosion resistance of ZG04Cr13Ni4Mo martensitic stainless steel were studied by microstructure observation, mechanical properties and electrochemical properties tests. The results show that with the increase of Cr content, the yield strength gradually decreases and the elongation gradually increases,while the tensile strength of the material remains basically unchange after 620 ℃ tempering. For the corrosion resistance, with the increase of Cr content, the pitting corrosion resistance of the material increases gradually. When Cr content increases from11.5% to 12.0% and from 13.5% to 14.0%, the pitting potential increases in a jump manner. With increase of Cr content, it can improve the protective performance of passive film slightly, and significantly reduce the growth rate of steady-state pitting.