The sulfate content in acid mine wastewater (AMD) is generally high in China, and it is of great significance to remove sulfate in AMD. In view of the good application prospect of steel slag treatment for AMD, this paper analyzes the effect and mechanism of sulfate removal in steel slag treatment. The results show that the size of steel slag, AMD pH value, solid-liquid ratio and the initial sulfate concentration could affect the sulfate removal efficiency. When the steel slag particle size, pH, solid-liquid ratio and initial sulfate concentration were less than 75μm, 2, 70 g/L and 2000 mg/L, the highest sulfate removal rate was 79.15%, and the adsorption capacity was 36.79 mg/g. The kinetic analysis and mechanism analysis showed that the sulfate removal conforms to the quasi-second-order kinetic model and Freundlich isothermal adsorption model, while the interaction between sulfate and steel slag is mainly multilayer chemisorption, accompanied by chemical precipitation, electrostatic adsorption and surface complexation.