At the late stage of water flooding，the invalid circulation of injected water in fault-block reservoirs makes it difficult to increase pressure. The proposed combined flooding technology of CO2 gas cap and artificial edge water is considered as an effective solution to this problem. In order to study the pressure recovery of combined flooding reservoir，the relationship between pressure recovery rates and injection rates，as well as the optimization of water injection rate，gas injection rate and injection time were studied. Indoor experiments were conducted to evaluate the qualitative relationship of pressure recovery rates with gas injection volumes/rates and injection rate ratios between gas and water. Based on numerical simulation，single-factor analysis and orthogonal experiment design were combined to verify the experimental results. The quantitative relationship of the pressure recovery rates with the above three factors was established by response surface analysis，and the correlation prediction model was regressed. Finally，the technical policies for combined flooding were comparatively optimized. The research results show that the combined flooding effect is positively correlated with the injection rates，gas injection volumes/rates，and injection rate ratios between gas and water，and it is most sensitive to the gas injection rates. There are optimal gas/water injection rates for combined flooding and an optimal matching relationship between them，and then a chart for determining the injection timing for combined flooding is given.