In this paper a micro multi-phase flow equation is built based on the mechanism of a multi-phase fluid flow in porous media. The authors consider the impact of convection diffusion and the improved component mixing rule. In order to accurately evaluate the fluid flow in a low permeability reservoir, two models are established to simulate simple pore throat structure and complex pore throat structure. The predicted residual oil distribution characteristics of CO(2)flooding in low permeability reservoir, calculated by finite element microsimulation, have been further verified by experiment. Furthermore, we analyze the effect of different wettability on microflow characteristics of CO(2)flooding. The results show that CO(2)flooding improving microsweep volume by convective diffusion is more evident in low permeability reservoirs than in high permeability reservoirs. The residual oil is mainly distributed following a pattern of prismatic, wedge-shape, or membrane microstructure. With decrease in the wetting angle on the fluid-rock boundary, the efficiency of oil displacement is further improved.