Through molecular dynamic simulations, the mechanism of CO2 extracting hydrocarbon in rough surface was investigated. In the present study, the entrance effect of CO2 molecules and the destruction of the miscible zone were considered as the critical factors in the extraction process. Subsequently, seven assistants were added to explore the main factors of the stability of miscible zone. The parameters of viscosity and solubility were chosen to characterize the properties of displacement agents and the dissolving capacity of CO2 was proved to be the key to improving tight oil recovery in nanopores. In addition, when the roughness of the surface was adjusted from 2.2 to 3.9, the effects of the injection pressure on residual oil were different, laying emphasis on the significance of reservoir structure for CO2 to enhance oil recovery. Moreover, our work also provided a molecular-level understanding of the CO2 extraction of hydrocarbon in rough surface, and the results had some promise for the enhancement of oil recovery in CO2 displacing engineering.