Abstract: In flotation the copper-molybdenum bulk concentrate is difficultly separated. The reason is that the contents of molybdenite and copper distribution in the -0043mm of bulk concentrate are 77.30% and 65.77%,respectively. In the experiment, the bulk concentrate is firstly thickened and dereagented, then add sodium silicate and NaHS as depressor of the gangue and copper minerals; add oxidant potassium permanganate to depress the ultra-fine size secondary copper minerals. With the condition of fine size (82.5% passing 0.043 mesh) and the closed water circuit, the closed process of experiment is one roughing, two scavenging, four cleaning, two cleaning after scrubbing. The effective copper and molybdenum separation is achieved. The grade of molybdenum concentrate is 55.73% Mo, 0.64% Cu with recovery of 68.11%; while the grade of copper concentrate is 21.36% Cu, 0.1447% Mo with recovery of 99.98%.