Experimental research is carried out on the ore-dressing processes for ores from deep in a large-scale molybdenum mine in Heilongjiang,investigates the effect of flotation flowsheet structure,reagent regime,grinding fineness on flotation index.The results show that under optimal parameters,the process of molybdenum roughing-roughing concentrate regrinding and cleaning-sulfur separation from roughing tails can obtain the molybdenum concentrate with molybdenum grade of 50.800 %,molybdenum recovery rate 82.59 %,and the sulfur concentrate with sulfur grade of 44.640 %,sulfur recovery rate 69.98 %,which are good indexes.