This study investigated the enhancing effects of graphene oxide (GO)/iron series, specifically GO/Fe 0, GO/Fe 3O 4, and GO/Fe 2O 3, on anaerobic treatment of sulfate-laden organic wastewater at varying chemical oxygen demand to sulfate (COD/SO 4 2-) ratios, combined with an analysis of co-metabolic microbial communities. Our results indicate that all GO/iron series significantly improved COD Cr and SO 4 2- removal efficiencies and methane production. Furthermore, they optimized the system’s pH and oxidation-reduction potential (ORP) and enhanced the physicochemical properties of the activated sludge. The enhancement effect was more pronounced at lower COD/SO 4 2- ratios, with GO/Fe 0 exhibiting the most significant improvement. Metagenomic sequencing revealed that the addition of GO/iron series maintained the stability of the microbial community structure, thereby conferring stronger shock resistance to the system. This research provides a scientific basis for exploring the application of anaerobic systems in treating sulfate-containing organic wastewater.