Situated in the Awulale metallogenic belt of Western Tianshan Mountains, the large-sized Chagangnuoer magnetite deposit is contained within volcanic-sedimentary rocks of the Carboniferous Dahalajunshan Formation. Due to the lack of studies in ore deposit geochemistry for this deposit, this paper aimed to conduct systematic stable isotope analyses of C, O and S by isotope mass spectrometry method for minerals of magnetite, pyrite, chalcopyrite and calcite chosen from various mineralization stages. Crystallization differentiation of magmatic fluid was the dominant mineralization on the early ore-forming stage, whereas prograded and retrograded alterations were the crucial factors in iron enrichment and mineralization on the later stage.