In light of the property change of a porphyry copper-molybdenum ore in Inner Mongolia that leads to sticky foam and unsatisfying flotation index in the copper-molybdenum mixed flotation process,experimental research on the copper-molybdenum mixed flotation is carried out.The results show that when the grinding fineness -0.074 mm accounts for 60 %,CG705 is used as regulator,and the closed circuit of once roughing,three times cleaning,three times scavenging and middling recycling in order is adopted,the mixed concentrates with copper grade 19.250 %,molybdenum grade 1.360 %,copper recovery rate 84.24 % and molybdenum recovery rate 51.13 %.The research solves the challenges in the mixed flotation process of the ore in a good way.