The purpose of using a mixed collector is to increase both flotation efficiency and selectivity. The mixed collector of potassium isopentyldithiocarbonate and N-dodecyl mercaptan exhibits high efficiency for the flotation of auriferous arsenopyrite, and the 2:1 mixing mass ratio of potassium isopentyldithiocarbonate and N-dodecyl mercaptan is preferred. Batch flotation tests indicate that a concentrate with the grade of 47.58 g/Mg Au and the recovery of 86.45% Au is achieved by using the mixed potassium isopentyldithiocarbonate/N-dodecyl mercaptan in weakly alkaline pulp. The collector mixture potassium isopentyldithiocarbonate + N-dodecyl mercaptan has greater adsorption density on the arsenopyrite surface than other conventional mixed collectors. The mixed potassium isopentyldithiocarbonate/N-dodecyl mercaptan can adsorb onto the arsenopyrite surface by intense chemisorptions, and the Sulfur-Iron chemical complexation is considered as the main adsorption mode. This is the reason why mixed potassium isopentyldithiocarbonate and N-dodecyl mercaptan collector can improve the flotation efficiency of auriferous sulfides.