This article covers a hydrometallurgical method for processing of a gold-antimony flotation concentrate in alkaline sulfide solutions. Thermodynamic analysis of the reaction stibnite with sulfide sodium and sodium hydroxide was performed. The chemical and phase compositions of the investigated material, mainly represented by compounds of antimony, silicon, calcium, sulfur and iron are studied. Phase composition: quartz, stibnite, quicklime, pyrite, dolomite and arsenopyrite. The dependences of the influence of sulfide sodium and sodium hydroxide concentration, and the liquid to solid ratio on antimony extraction into solution were determined by methods of mathematical experiment planning. The calculated values ​​of the determination coefficients testify to the adequacy of the chosen two-level model. The optimum parameters of the process were obtained: L/S ratio = 4,5; the nitric acid sulfide sodium concentration was 61.09 g/L; sodium hydroxide concentration was 16.47 g/