Viscosity reduction experiments of new Gemini surfactant RB107 was done to solve the problems of high content of colloid and asphaltenes in formations，high viscosity of heavy oil and low recovery efficiency of water flooding in offshore S oilfield. Emulsion concentration，aggregation morphology，interfacial activity，wettability，stability and other properties of the surfactant were evaluated and its oil displacement performance was investigated through physical simulation experiment. When mass fraction is 0.3% and oil-water volume ratio is 50∶50，the viscosity of the heavy oil may be decreased by 97% and oil-water interfacial tension may be dropped to 0.165 6 mN/m under the condition of oil reservoir. The results show that RB107 has strong performance of viscosity reduction and interfacial activity under low concentration. RB107 also has fast emulsification speed（0.24 mL/min）and strong stability with uniformly dispersed oil-water emulsion droplets of small diameter. Contact angle of RB107 solution was 10.8° on oil base，which shows that RB107 has a strong wettability on the oil-water interface. Compared with water flooding results，physical simulation results of RB107 could enhance the oil recovery by 10.1%. RB107 could be the viscosity breaker of the heavy oil in S oilfield for its good viscosity reduction effect.