Abstract: There are micro-fine mud existed in rough molybdenum concentrate separated from copper-molybdenum ore with a hydrocyclone in a dressing plant of Tibet and large amounts of micro-fine mud in tailing 1 of molybdenum separation.Treating the two kinds of micro-fine mud separately is an effective measure to solve the non-ideal result about copper-molybdenum separation.Under the condition of low pulp density，beneficiation on the refractory copper-molybdenum sample with micro-fine size and high degree of mud is carried out.The results show that the sample with Cu and Mo grade of 23.12% and 2.98% is treated by the closed-circuit process of one-roughing，four-cleaning，one-scavenging and middles back to the flow-sheet.By this method，Mo concentrate with Mo grade of 44.97%，and Mo recovery of 86.46%，and Cu of 1.17%，and Cu concentrate with Cu grade of 24.45%，Cu recovery of 99.71%，and Mo of 0.43% were achieved separately with good Cu-Mo separation effect.

Key words: Micro-fine grain, Mudding, Copper-Molybdenum separation, Low pulp density flotation