The preparation of sodium thiomolybdate from sodium tungstate solution using S as a sulphidizing reagent was studied. The experimental results indicate that sodium molybdate in sodium tungstate solution can be very effectively converted to sodium thiomolybdate by using S as a sulphidizing reagent, and that the sodium thiomolybdate can be adsorbed by D290 resin, so as to separate thiomolybate from sodium tungstate solution, and that S was proved to be a desirable and suitable sulphidizing reagent for separation of molybdenum from tungsten. The conditions of proceeding sulphidization of MoO42-, such as the mass ratios of S to molybdenum, the heating times and temperatures, the concentrations of NaOH. The yield of sulphidization of MoO42- in the sodium tungstate can be reached over 96% for commercial feed solution containing WO3 120.257 g·L-1, and Mo 1.457 g·L-1 under the optimum conditions. The preparation of sodium thiomolybdate from sodium tungstate solution using S as a sulphidizing reagent was studied. The experimental results indicate that sodium molybdate in sodium tungstate solution can be very effectively converted to sodium thiomolybdate by using S as a sulphidizing reagent, and that the sodium thiomolybdate can be adsorbed by D290 resin, so as to separate thiomolybate from sodium tungstate solution, and that S was proved to be desirable and suitable sulphidizing reagent for separation of molybdenum from tungsten. The conditions of proceeding sulphidization of MoO42-, such as the mass ratios of S to molybdenum, the heating times and temperatures, the concentrations of NaOH. The yield of sulphidization of MoO42- in the sodium tungstate can reached over 96% for commercial feed solution containing WO3 120.257 g · L-1, and Mo 1.457 g · L-1 under the optimum conditions.