Abstract: A novel preformed particle gel (PPG) as a chemical EOR was screened out by means of the rheometer, interfacial tensiometer, laser particle analyzer, microscopic oil displacement and physical simulation of oil displacement. The present paper evaluated its properties in application, investigated the mutual interaction between the PPG and other polymers or surfactants, designed a heterogeneous combination flooding system (HCFS), and appraised the EOR effect of this new system under the condition of high-temperature, high-salinity and after-polymer-flooding reservoirs in the Shengli Oilfield. The results indicated that PPG could not only migrate and penetrate through porous mediums, but also generate a more significantly sweeping efficiency by means of piling up, plugging, pressure rising and deforming at throats to modify the existing dominant migration paths, and it was of a greater volumetric-expansion capacity than conventional polymers. Because the combination of the PPG and polymers could enhance the viscosity and viscoelasticity of a system, the heterogeneous combination flooding system (HCFS) composed of the PPG, surfactants and other polymers is of a displacement efficiency similar to the combination flooding. Under the experimental condition of a dual sand-packed tube flooding with the interlayer heterogeneity of (1000∶5000)×10^-3 μm², the HCFS could improve the oil recovery by 22.5% for HT/HS reservoirs in the Shengli Oilfield and by 19.1% for the Ng3 reservoirs after polymer flooding in the Zhong-1 section of the Gudao Oilfield.