Most of PI formation reservoir in Daqing Oilfield has entered the subsequent water flooding stage, the cumulative recovery rate is about 57%, and more than 40% of geological reserves are still reserved in underground. After polymer flooding, the dominant seepage channels of PI formation reservoir appeared generally, but the inefficient circulation exist and get more serious. Based on coring, well logging and injection?production dynamic changing data, it is found that the dominant seepage channels are mainly formed at the bottom of the PI2 and PI3 units vertically, as well as interior of channel sandbodies on the plane parallelling to the paleocurrent direction. The thickness of the dominant seepage channel accounts for 10.6%, the remaining reserves 7.8%, and the water absorption proportion as high as 60.2%. In order to effectively block the dominant seepage channel after polymer flooding and decrease the inefficient circulation, PPG particles with high elasticity and strength were developed. The results of indoor flow experiments show that PPG particles have superior shear resistance performance and can flow into the deep reservoir to block the dominant seepage channel. The oil displacement experiments indicate that the enhanced oil recovery of PPG / weak base ASP flooding system can reach 15.6%, which is 3.3% higher than that of weak base ASP flooding, saving 28% of polymer consumption. The results in provide strong technical support for the continuous and efficient development of oilfield.