Interfacial effects and intermolecular forces dominate in shale nanopores，and the classical theory of continuum medium mechanics has limitations or even failures，thus becoming a key issue limiting the development of shale oil and gas storage and flow theories，as well as mathematical simulations. In order to address this issue，the interaction between alkane molecules in shale oil and graphene walls in shale nanopores and the adsorption/retention characteristics of multi-component alkanes in shale oil were studied. By using molecular dynamics simulation，single-component and multi-component systems of shale oil were constructed to analyze the adsorption behavior and retention phenomena of different alkane molecules in the pores，as well as the effects of van der Waals forces，pore sizes，and other factors on the strength of the interactions and the characteristics of adsorbed layers. The simulation results show that the interaction strength between alkane molecules and graphene walls increases nonlinearly with the increase in the number of carbon atoms in alkane molecules due to the irregularity of molecular arrangement and nonlinear van der Waals forces. In the single-component system of shale oil，the number of adsorption layers of alkane molecules increases with the increase in the interaction strength between alkane molecules and graphene walls，but the adsorption strength gradually decreases with the increase in the number of adsorption layers；in the multi-component system of shale oil，there are obvious component differentiation and heavy hydrocarbon retention phenomenon.