The invention discloses a rosinyl quaternary ammonium salt dimeric surfactant as well as a preparation method and application thereof. The molecular structural formula of the rosinyl quaternary ammonium salt dimeric surfactant is as shown in the specification, wherein R is a rosinyl tricyclic phenanthrene structure, and n is equal to 3, 4, 5 or 6. The rosinyl quaternary ammonium salt dimeric surfactant which takes rosin as a raw material satisfies the demand of environment-friendly raw materials for preparation of the surfactant. The surfactant prepared by the invention has good surface activity and antibacterial activity. The CMC (Critical Micelle Concentration) value of the surfactant is (2.28-3.38)*10<-5>mol/L, the gamma cmc value is 24.7-32.3mN/m, and the Krafft point ranges from 12 to 23 DEG C. The time of separating turpentine and water in an aqueous emulsion is 42-53 hours. The initial foaming height is 128-137mm. The foam height in 5 minutes is 121-131mm. The antibacterial activity of the surfactant to escherichia coli is superior to that of the marketed bacteriostatic agent bromogeramine.