Abstract: There is a large amount of CO₂ in the produced fluid from CO₂ flooding, and a lot of foam is formed in the process of gas and liquid separation. In this paper, the effects of internal components of separators on the separation characteristics of CO₂ flooding produced fluid were discussed by performing numerical simulation on the separation characteristics of internal flow deflector and defoaming plate of horizontal separators. The physical property parameters of produced fluid in the operating condition of separator were fitted, and the flow deflector inside the separator was numerically simulated in the conditions of four laying angles (15°, 30°, 45°and 60°) by using the multiphase-flow mixture model in CFD. It is indicated that the larger the laying angle of flow deflector is, the more favorable it is for gas and liquid separation, but the effect diminishes gradually. When the utilization stability and service life of flow deflector is taken into consideration comprehensively, the optimal laying angle of flow deflector is 45°. Finally, separators equipped with 1-3 defoaming plates were numerically simulated by using the mutual coupling between Population Balance Model (PBM) and CFD multiphase flow model. It is shown that defoaming efficiency increases as the number of defoaming plates inside the separator increases. The research results provide the basis for the design of high-efficiency separators used for CO₂ flooding produced fluid.