In this study, the effect of pH shock during the treatment of sulfate-containing organic wastewater was investigated using an anaerobic fermentation system reinforced with graphene oxide (GO)/iron series systems. The results show that the anaerobic system with the GO/iron series systems exhibited enhanced resistance to pH shock. Among them, the GO/Fe⁰ system had the strongest resistance to pH shock, the systems of GO/Fe₃O₄ and GO/Fe₂O₃ followed close behind, while the blank system performed the worst. After pH shock, the COD_Cr removal rate, SO₄²⁻ removal rate, and gas production of the GO/Fe⁰ group were significantly improved compared with those of the control group by 51.0%, 65.3%, and 34.6%, respectively, while the accumulation of propionic acid was the lowest. Further, detailed microbial characterization revealed that the introduction of the GO/iron series systems was beneficial to the formation of more stable anaerobic co-metabolic flora in the system, and the relative abundance of Geobacter, Clostridium, Desulfobulbus and Desulfovibrio increased after acidic and alkaline shock.