Abstract: Since extra-low permeability and heterogeneous reservoirs are characterized by low porosity, low permeability, low saturation and low production, utilizing conventional water flooding has big development difficulties and low recovery ratio, while CO2 flooding can improve the recovery percentage of extra-low permeability and heterogeneous reservoirs significantly. According to the geological and reservoir characteristics of extra-low permeability and heterogeneous reservoirs, and double-layer heterogeneous cores were used to simulate the heterogeneity of reservoirs and displacement experiments under 5 different gas injection rates (1, 2, 4, 8 and 10 mL/min) were designed and completed for systematic analysis of the influence of CO2 flooding on oil recovery ratio. Research results indicate that the largest recovery ratio increase by CO2 flooding occurs before CO2 channeling, and as the gas injection rate rises, the advance rate increases and breakthrough time leads forward gradually. Reasonable rate of displacement makes contacting time of CO2 and water and crude oil in the core porosity, and recovery ratio be improved, and thus improves the economic benefits of the development of extra-low permeability and heterogeneous reservoirs.