Tin was recovered in metal from an industrial tin-bearing byproduct containing Na2SO4 by carbothermic reduction smelting, and the effects of basicity (Na2O/SiO2), temperature, and reaction time on the recovery of tin were studied. Na2SO4 was reduced by carbon and formed into sodium silicate slag (Na2O–SiO2) in the presence of SiO2. Tin content in slag decreased with the increase of Na2O/SiO2 ratio in slag, temperature, and reaction time, but the recovery of tin was affected by volatilization of tin in high temperature and high silica region of basicity. In this study, the maximum recovery rate of tin was 94.8% at the experimental condition of 1200 °C, 2 h, and 0.55 of Na2O/SiO2 ratio. The major impurities in produced metal were Bi, Pb, Cu, Fe, and most of Bi, Pb, Cu were distributed to the metal phase, but the distribution of Fe was closely related to basicity.