Abstract: The effect of sulfur on the migration and transformation of heavy metals （Zn, As, Cu, Mn） during the co-processing of solid waste, as well as its underlying mechanisms, is aimed at being investigated. The introduction of sulfur during co-combustion of solid waste influences the chemical forms and distribution of heavy metals, which in turn has significant implications for both environmental impact and the safe operation of equipment. The research methods include thermodynamic equilibrium calculations using FactSage software to simulate the sulfur species at different temperatures and analyze the impact of sulfur on heavy metals. Engineering experiments were also conducted by combusting mixed fuels in a fluidized bed boiler, collecting samples of flue gas, slag, fly ash, and gypsum, and measuring the heavy metal content to analyze their distribution characteristics. The results show that sulfur predominantly exists in a gaseous form during combustion and significantly affects the chemical speciation of heavy metals. Under high-temperature conditions, sulfur reacts with heavy metals to form sulfides or sulfates, and the presence of sulfates promotes the formation of silicoaluminate phases. This silicoalumination process plays a positive role in the stabilization of heavy metals. The leaching concentrations of Mn, As, Cu, and Zn in the solid products are all below the detection limit. The leaching behavior of heavy metals is related to the formation of sulfides. An increase in sulfur content favors reactions that form stable phases such as spinel. Sulfur not only alters the volatility and chemical speciation of heavy metals in the co-processing of solid waste but also plays a critical role in the environmental impact of solid waste treatment. By optimizing sulfur management and treatment strategies, the environmental risks associated with heavy metals can be effectively reduced, while improving the safety and efficiency of solid waste treatment.