Abstract: During the boiler co-processing process, the chlorine element significantly affects the migration and transformation characteristics of heavy metals. The distribution characteristics of chlorine and heavy metals during the co-processing of solid waste are investigated by combining engineering experiments and thermodynamic equilibrium calculations. Thermodynamic calculation results show that, within the temperature range of 800 ℃ to 1500 ℃, chlorine mainly exists in gaseous forms such as Cl₂, Cl, and HCl, and promotes the formation of volatile metal chlorides, such as CuCl₂（g） and ZnCl₂（g）, when co-existing with chlorine. As the temperature increases, the mass fraction of metal chlorides significantly rises. Engineering experimental results show that Cu, Zn, and As are mainly distributed in fly ash, with a distribution rate exceeding 99%, indicating that these heavy metals are prone to volatilization during combustion. Mn, on the other hand, has relatively low volatility, and a higher mass fraction of Mn is found in the gypsum. Leaching tests on heavy metals in solid products show that the leaching concentration of As in slag is more than three times that of As in gypsum, while the leaching concentrations of Zn, Cu, and Mn in gypsum are significantly higher than those in fly ash and slag. The leaching concentrations of all heavy metals in the tests are far below the limit standards in China, indicating a low potential environmental risk under the current process conditions. In the boiler co-processing process, chlorine enhances the volatilization and leaching characteristics of heavy metals, but the overall environmental risk remains low.