CO₂ flooding is an effective technical measure for tertiary oil recovery in high water cut reservoirs. Using the existing well pattern to inject CO₂ is an economical and feasible development method under low oil price. Although the particle migration caused by the displacement process will block the pore throat of rock，the injection of CO₂ can effectively reduce the injection pressure，and the dissolution occurred during the injection process improves the seepage capacity of fluid as a whole. By carrying out the experiment of particle migration plugging law after CO₂ flooding and the evaluation experiment of CO₂-aqueous solution on rock dissolution，and evaluating the variation characteristics of relative permeability curves before and after displacement，the influence of CO₂ flooding on reservoir seepage capacity was further explained. The results showed that during the injection of CO₂， the injection pressure decreased when the injection rate was 0.1 mL/min and 1.0 mL/min. The core permeability loss was 37.05% after CO₂ flooding under the condition of oil，while the core permeability recovery was 30.48% after cleaning the core with toluene and anhydrous ethanol，indicating that the particles would be bound by crude oil during the migration process，accumulate into clusters，and cause blockage. Although there was a certain blockage，the CO₂-aqueous solution mainly reacted with chlorite and released Ca²⁺，Mg²⁺，Fe²⁺ and other ions. The concentration of Ca²⁺ increased by 137.05%，the concentration of Mg²⁺ decreased by 52.20%，and then the concentration of Fe²⁺ decreased by 49.45%. It showed that although the generated MgCO₃ and Fe₂O₃ would block the pore throat of rock，the dissolution of CaCO₃ by CO₂ was stronger，which improved the seepage capacity of the fluid as a whole，thus improving the water injection capacity and the effect of subsequent water flooding to a certain extent. The irreducible water saturation in the relative permeability curve before and after CO₂ flooding increased，the residual oil saturation decreased，the two-phase seepage area increased，and then the oil displacement efficiency increased. It further indicated that the dissolution produced by CO₂ flooding increased the pore space and seepage channel as a whole，and then improved the injection capacity of injected water.