Abstract: In order to explore the synergistic mechanism of mixed collector in enhancement of flotation of low-rank coal, test is made on flotation of low-rank coal through combined use of dodecane (C12) and cocaminopropyl betaine (CAB) as mixed collector. Through measurement of the surface tension of the mixed collector and the contact angle of coal particle surface under the action of the collector as well as molecular dynamics simulation, the mechanism of mixed collector in enhancement of flotation of low-rank coal is brought to light. Test result shows that the use of mixed collector can lead to improvement of low-rank coal flotation effect and a best result can be expected when C12 and CAB are used at a ratio of 3∶1 (by volume); under such an optimum condition, the yield of concentrate, recovery of combustible matter and flotation efficiency can go up to 70.83%, 79.17%and 31.22% respectively; the surface contact angle of low-rank coal particle is noticeably increased due to decrease of surface tension of mixed collector; and the water binding force on coal surface is weakened because of decrease of absorption distance of mixed collector on coal surface.