Abstract: The effect of Cl^-, SO₄^2- and pH on pitting behavior of 304 stainless steel in simulated ash water of coal chemical industry was studied through electrochemical test and dipping test by potential scanning technology, AC impedance technology and scanning electron microscopy analysis. The results show that in test condition, the pitting degree of tested steel increased with increase of Cl^- content in the simulate ash water and the tested steel had the lightest pitting degree when mass fraction of Cl^- was 300 mg·kg^-1. With increase of SO₄^2- content in the simulate ash water, the pitting degree of tested steel decreased. When mass fraction of SO₄^2- was 2 000 mg· kg^-1, the tested steel had the lightest pitting degree. With increase of pH in the simulate ash water, the pitting degree of tested steel decreased. The tested steel had the lightest pitting degree when the pH was 10.