Abstract: Smelting process is an effective way to treat industrial dust and fly ashes nowadays.In order to effectively control the remove and recovery of heavy metals such as Zn,Pb by smelting process,the vaporization behaviors from FeO-CaO-SiO₂-Al₂O₃-Fe₂O₃ slag system with Cl were analyzed and compared in this study.Firstly,thermodynamic prediction on the possible vapor species of Zn and Pb in molten slag was carried out,together with the effect of some factors such as temperature,slag compositions and oxygen potential.And then related experimental study was performed.Finally the various technical measures and optimized parameters for enhancing the volatile efficiency of zinc and lead were determined.