The performance of ASP （alkali/surfactant/polymer）was studied in the aspects of viscosity，interfacial tension ，molecular clew dimension（D_h）， molecular configuration ，flooding effect and their influencing factors. The mechanism of enhancing oil recovery was analyzed. The results showed that the viscosity of ASP system decreased from 246.9 mPa·s to 138.8 mPa·s，the interfacial tension decreased and D_h fell from 324.7 nm to 263.5 nm when the mass fraction of NaOH increased from 0 to 1.2%. As the dosage of surfactant increased from 0 to 0.3% ，the viscosity of ASP system decreased from 127.0 mPa·s to 122.1 mPa·s and then increased to 138.8 mPa·s，the interfacial tension decreased and D_h increased from 139.7 nm to 263.5 nm. As the mass ratio of solid to liquid and adsorption times increased，the interfacial tension of ASP system increased. In alkali/polymer system ，structural morphology of polymer molecules gave priority to“sheet”，the“nets ”came with complementary. In heavy alkyl benzene sulfonate/polymer system ，there appeared a big area of“bead ”for structural morphology of polymer molecules ，however，structure of “nets ”wasn’t obvious. In ASP system ，structure of “nets-sheet ”presented for structural morphology of polymer molecules. The results of oil displacement experiment showed that the recovery efficiency increment of ASP system，polymer solution and alkali/surfactant system was 14.8% ，12.2% and 4.8% respectively in comparison to water flooding. With increasing viscosity of oil-displacement agent，the chemical recovery efficiency increased ，but its increment decreased gradually. When the mass fraction of polymer was 0.12% ，0.18% and0.25% ，the recovery efficiency increment of polymer flooding was 12.2% ，15.8% and 18.7% ，and that of ASP flooding was14.8% ，18.3% and 21.0% ，respectively. In the condition of same polymer dosage，the recovery efficiency increment of ASP flooding was higher than that of polymer flooding by 2.3% —2.6% . The contribution of the effect of oil-displacement agent on enlarging swept volume to recovery efficiency was greater than that on improving oil-displacement efficiency to recovery efficiency.