In order to improve the comprehensive utilization of iron sulfide minerals in the abandoned mine in Inner Mongolia, this study focused on making full use of the effective components of pyrite and pyrrhotite to treat Cr-containing wastewater. The optimal experimental conditions were found. Compared with the previous studies, the grain size of samples used in this study was lowered to 80~100 mesh, the dosage was decreased by 70%, and the concentration of chromium-containing wastewater treatment was increased to 50 mg/mL. It is worth mentioning that most of the Cr(Ⅲ) appeared in Cr₂S₃ phases by XPS scanning analysis after the treatment of Cr(Ⅵ)_containing wastewater by natural pyrite and pyrrhotite. The content of Cr₂S₃ accounted for 77.99%, 86.53 and 100% of total chromium phase respectively when natural pyrite was use to deal with Cr(Ⅵ) under the reaction system whose pH values were 1.84 and 4.15 and 10.87. There also appeared a considerable amount of trivalent chromium in Cr₂S₃ phase after using pyrrhotite in the pH of 6.5 and using modification pyrite heated under the condition of 500℃ and pH 4.15. The removal rate for processing directly the tannery of actual wastewater containing Cr(Ⅲ) was up to 73% when the optimum conditions obtained in this study for the treatment of Cr(Ⅵ) were directly used. This research provides a means for the comprehensive treatment of Cr(Ⅵ) and Cr(Ⅲ), and it has become one of the ways of producing useful resources in the course of mining.