Abstract: Two-phase displacement in porous media is a physical phenomenon commonly observed in nature and industrial fields, and CO2 flooding technology is a common means to enhance oil recovery in unconventional energy development. Based on the multiphase, multicomponent, and multiple-relaxation-time lattice Boltzmann method (LBM), this work couples the Shan-Chen pseudopotential multiphase flow model with displacement boundary conditions to propose an improved multiphase flow displacement LBM. Using this method, comparative validations are conducted for interfacial tension, contact angle, and the diffusion process of CO2 in the oil phase. The Péclet number is introduced to establish quantitative characterization relationships among the diffusion coefficient, Péclet number, and CO2-oil interaction parameters. Furthermore, numerical simulations analyze key parameters in the CO2 displacement process and quantitatively evaluate the displacement efficiency under the influence of different key parameters. The results show that for CO2 immiscible displacement, the combined effect of capillary number and viscosity ratio significantly influences the displacement efficiency after CO2 breakthrough, and different wettabilities affect the immiscible displacement effect and the distribution pattern of remaining oil. For CO2 miscible displacement, the displacement efficiency and oil recovery rate are the lowest at a low Péclet number; a high Péclet number enhances displacement instability, leading to a gradual decrease in displacement efficiency. When the Péclet number is around the unity, the synergistic coupling effect of molecular diffusion and viscous flow is maximized, maintaining a high displacement efficiency. The influence mechanism of the Péclet number has certain viscosity dependency: for different viscosity ratios, a smaller Péclet number can effectively suppress the viscous fingering caused by them. Compared with CO2 immiscible displacement, miscible displacement can effectively improve oil recovery in the actual development of tight oil reservoirs due to lower interfacial tension and oil viscosity.