The international research progress of the diffusion coefficient of CO2 in reservoir fluids was reviewed. The measurement principle and experimental methods for diffusion coefficient of gas in liquid were summarized. The advantages and disadvantages of common methods were compared, and the applicability of these methods in the diffusion process of CO2 in reservoir fluid was studied. The diffusion coefficients of CO2 in various reservoir fluids were listed, the main affecting parameters and variation of diffusion coefficients were discussed, and some typical correlations of diffusion coefficients were proposed. Finally, in view of the domestic reservoir condition and the lack of diffusion research, the optimization of experimental methods under high pressure high temperature was discussed, which provided a reference for future research.