The application scale of heterogeneous combination flooding has been expanding significantly since the pilot test carried out at Ng3 of Zhongyi area，Gudao Oilfield，Shengli Petroleum Province in 2010. It has become one of the leading chemical flooding technologies for further enhancing oil recovery in old oilfields. Although the application of heterogeneous combination flooding technology has achieved successful results at Ng3 of Zhongyi area，the remaining oil distribution and reservoir response law after heterogeneous combination flooding are still the key problems to be addressed in the promotion and implementation of the technology. This paper systematically analyzes the distribution characteristics of remaining oil after heterogeneous combination flooding based on sealed cored well and summarizes the reservoir response law by comparing the remaining oil distribution before and after heterogeneous combination flooding. The results show that the average remaining oil saturation at Ng3 of Zhongyi area is 28.3% after heterogeneous combination flooding. The samples with high remaining oil saturation mostly appear at the top of the positive rhythm reservoir and near the interlayer. The microscopic occurrence mode of remaining oil is mainly disseminated. Compared with that before heterogeneous combination flooding，the average remaining oil saturation is reduced by 7%，and the average displacement efficiency is increased by 13.1%. Moreover，the displacement is more balanced in the vertical direction，and the difference in remaining oil saturation between the top and bottom of the positive rhythm reservoir is reduced after heterogeneous combination flooding.