The effect of metal-inorganic complex depressant composed of aluminum sulfate and sodium silicate (AlSS) on the flotation separation of scheelite and calcite was studied. Zeta potential and adsorption measurements confirmed that the negatively charged colloidal particles composed of Al(OH)₄^- and SiO_m(OH) _n^4-2m-n tended to be adsorbed on calcite surface, inhibiting the adsorption of sodium oleate (NaOL), while the adsorption of negatively charged colloidal particles on scheelite surface was relatively low, which resulted in the great adsorption capacity of NaOL on scheelite. The contact angle measurements showed that the hydrophobicity of scheelite was significantly better than that of calcite in the NaOL+AlSS solution. XPS measurement results indicated the adsorption of Al and Si on the calcite surface rather than on the scheelite surface. Compared to adding water glass (sodium silicate, SS) only, the depression effect on calcite was significantly enhanced by the combination of AlSS, while scheelite flotation was hardly affected. Scheelite concentrate with WO₃ grade of 68.34% and WO₃ recovery of 83.14% could be obtained from mixed scheelite and calcite ores by adding AlSS.