In order to qualitatively study the displacement effect of polymer/surfactant composite system on heavy oil，the oil displacement process of the composite system in homogeneous microscopic glass model was observed by microscope，and the residual oil distribution in the image was analyzed by image processing technology. The recovery rate was calculated and the microscopic oil displacement mechanism of the composite system was analyzed and compared with that of surfactant，polymer and water flooding. The results showed that the recovery rate of water flooding could reach 56.94%，and the residual oil mainly existed in the form of column，oil droplet，membrane，blind end oil and cluster，etc. The residual oil of surfactant flooding was existed in the form of blind end and cluster，and the enhanced oil recovery rate of 1% anionic surfactant（BCJ-11）flooding was 29.46%. The residual oil of polymer flooding was mainly existed in the form of filament and oil film. The enhanced oil recovery rate of 100 PV 1500 mg/L partially hydrolyzed polyacrylamide（C6725）was 22.12%. The residual oil of composite flooding existed in the form of oil film. The enhanced oil recovery rate of composite system consisting of 1500 mg/L C6725 and 0.8% BCJ-11 was 34.59%. For several types of residual oils bound in the pores，the viscoelasticity and low interfacial tension of polymer/surfactant flooding system could cause the oil phase interface to form filaments for continuous migration. The composite flooding system displaced the residual oil in a wide range，and the washing efficiency of the affected area was high.