ASP flooding technology is being used in the second class reservoirs of Saertu oilfield in Daqing to improve the oil recovery after water flooding. In order to know the mechanism of ASP system driving remaining oil after water flooding，microscopic simulated model was built according to the real pore throat of casting body slice of the natural core and experiment of ASP flooding using this model was performed. The results show that，the main types of remaining oil after water flooding are the cluster type，the film type and the island type. There are also a little blind end type and the throat type. The ultra-low interfacial tension（IFT）and high viscoelasticity enable the ASP system to emulsify oil，drag the oil droplets into oil thread，peel oil film and sweep out the blind end oil，and therefore most of the cluster and the film type oil reduced while the island type oil increased，which improves the oil displacement efficiency. The quantitative analyses of oil displacement effect show that the water displacement efficiency is 50%，while the ASP displacement efficiency is 38.68%. The highest ultimate oil displacement efficiency of the microscopic models is 88.68%. The ultimate oil displacement efficiencies of the four ASP compound systems are all above 77%.