Abstract: The microstructure and corrosion resistance of S316 die steel were studied by X-ray diffraction(XRD), scanning electron microscope (SEM) and electrochemical workstation, and the pitting effect mechanism was analyzed.The results show that the microstructure of S316 die steel has changed from annealed ferrite to martensite after quenching at different temperatures, and M₂₃C₆ carbide still exists in S316 die steel at lower quenching temperatures (980 ℃and 1030 ℃).The passivation film thickness and pitting potential of quenched die steel are higher than those of annealed die steel, and the higher the quenching temperature is, the greater the passivation film thickness and pitting potential are.When the quenching temperature is 1130 ℃, S316 die steel has better pitting corrosion resistance, which is mainly related to the basic remelting of M₂₃C₆ carbide to the matrix and the thicker surface protective film.