Abstract: In order to improve the effects of waterflooding and polymer flooding in Pu125 block of Pubei oilfield, it is proposed to use polymer microsphere additive system to improve the technology. Under the simulated reservoir conditions, the performance of the additive system was evaluated, and its microstructure was analyzed to study its oil displacement effect. The experimental results show that the polymer microsphere additive system under the reservoir condition has a viscosity of 114.3 mPa·s, which has good temperature adaptability, mineralization adaptability and long-term stability. Its shear resistance is better than that of polymer solution; the microstructure of the additive system is that the microspheres are dispersed and adsorbed on the branches of the polymer network structure, which not only improves the viscosity of the polymer, but also enhances the dispersion of the microspheres; the efficiency of the additive system is better than that of polymer system. After the injection of the additive system, the distributing rates of the high and low permeability layers are about 50%, respectively. Compared with polymer-only flooding, the additive system can better improve the development effect and the recovery factor of high watercut reservoirs