Abstract: Due to the high energy consumption and environmental problems of sinter-blast furnace process of lead and zinc mixed concentrates, the use of bath smelting process instead of sintering process have become an alternative choice. The static method and XRD technique were used to study the effects of O₂ flow rate, temperature and burden composition on desulfurization of lead and zinc mixed concentrates as well as the phase change of molten slag. The research results show that the high temperature melt desulfurization of lead and zinc mixed concentrates has the advantages of short smelting time and high desulfurization rate. The increase of O₂ flow rate and reaction temperature was beneficial to the desulfurization reaction of lead and zinc mixed concentrates. The desulfurization rate of lead and zinc mixed concentrates decreased with the increase of Fe/SiO₂and CaO/SiO₂ mass ratio. However, when experimental temperature reached at 1 400 ℃, the increasing CaO/SiO₂ mass ratio was conducive to the desulfurization of lead and zinc mixed concentrates. The spinel phase (Zn_xFe_3-xO_4+y) was formed and increased with the increase of Fe/SiO₂ mass ratio, when experimental temperature was at 1 250 ℃.