Abstract: A molybdenum-bismuth polymetallic sulfide ore in Inner Mongolia contains high grade of molybdenum (0.65 %) and bismuth(1.12%) which has a high industrial recovery value. The process of "mixed flotation-separation of molybdenum-bismuth" was carried out to recover the useful minerals. The diethyldithiocarbamate and kerosene were used as collector in mixed flotation. The sodium sulfide and sodium sulfite were used as composite depressant and kerosene as collector for molybdenum-bismuth separation. The small closed-circuit test eventually obtains a molybdenum concentrate with 47.31 % of molybdenum and 89.52 % of molybdenum recovery and a bismuth concentrate with 42.64 % of bismuth and 86.04 % of bismuth recovery. The separation of molybdenum-bismuth is realized.