The invention discloses a combined collector for floatation of a porphyry copper-molybdenum mine and a floatation method thereof. The combined collector is characterized by at least comprising phthalate and carboalkoxy (aryloxy)-thiourea. The combined collector is used in a process of the floatation of the porphyry copper-molybdenum mine and the method comprises the following steps of: performingthe floatation on molybdenum, copper and the like in which the molybdenum is as a majority; floating molybdenite and part of copper sulfide minerals with high floatability so as to obtain a molybdenum and copper mixed concentrate with high a molybdenum recovery rate; and enhancing the recovery of the copper sulfide minerals with poor floatability. Due to the adoption of the combined collector andthe method, the problem of strong inhibiting effect on the molybdenite caused by a high-alkali environment of lime in a conventional mixed floatation process of the porphyry copper-molybdenum mine issolved effectively; and the method has the characteristics of simple and reasonable flow, high molybdenum recovery rate and the like.