Abstract: In order to solve the problems of large consumption of sodium sulfide， high COD contents in alkaline wastewater and high cost of wastewater treatment in Dexing Copper Mine， combined with the characteristics of fine particle size， simple component of minerals contained copper or molybdenum and high degree of monomer dissociation， the tests combined process of magnetic separation and flotation was carried out to bulk concentrate of copper and molybdenum. Through condition test， the better magnetic separation process parameters were determined. The magnetic separation extended test was carried out， and the magnetic separation results showed that the yield， copper grade and molybdenum loss rate of the concentrate were 39.16%， 29.27% and 6.08% respectively. The flotation separation test on magnetic separation tailings was carried out， and the flotation results showed that the molybdenum grade and molybdenum operation recovery rate were 46.54% and 93.97% respectively. The comprehensive calculation showed that the bulk concentrate containing 25.56% Cu and 1.04% Mo was treated by magnetic and flotation combined process，copper concentrate with Cu grade of 26.02% and recovery rate of 99.79% and molybdenum concentrate with Mo grade of 46.54% and recovery rate of 88.30% were obtained. The separation indexes of copper and molybdenum was very ideal. In addition， due to a yield of nearly 40% copper concentrate was separated by magnetic separation， the flotation amount was greatly reduced， the dosage of sodium sulfide and other flotation agents were reduced by more than 40%， the COD content of alkaline wastewater and the cost of water treatment were significantly reduced， which had significant economic and environmental benefits.

Key words: chalcopyrite, molybdenite, magnetic separation, flotation, dosage of sodium sulphide