The feasibility of using sodium sulfide as the sole modifier for the flotation of Xinhua molybdenite ore was examined. The potential mechanisms involved in the different flotation systems were discussed. The comparative flotation results reveal that in the kerosene-sodium silicate flotation system, better recovery and grade of the molybdenum are obtained using sodium sulfide as the slurry pH adjustment agent than using CaO. Under the optimal conditions (64 g/t kerosene and 6 kg/t Na2S), satisfied recovery and grade of molybdenite concentrate can be achieved (84% and 8.2%, respectively), indicating that sodium sulfide is a potential substitute modifier of sodium silicate. The open-circuit flotation test results further confirm the effectiveness of sodium sulfide which may render recycling the tailing water possible and make the flotation process more environmental acceptable and more economical due to the less use of kerosene and scavengers.