The availability of shale oil directly affects the degree of effective exploration and development, and the mobility of shale oil is closely related to its occurrence state. Therefore, studying the occurrence state of shale oil plays an important role in its development. The pore model is established by graphene and quartz, and the occurrence state of n-octane and its mixture in nanopores is studied by molecular simulation method. The effects of pore size, temperature, pressure, shale oil composition, wall wettability and wall composition on the occurrence state are analyzed. The results show that: ①shale oil is multi-layer adsorbed in the pores and symmetrical about the pore center, and the thickness of the adsorption layer is 0.4~0.5 nm; ②The larger the pore size of the reservoir, the higher the temperature, the lower the pressure, the lighter the molecular component, the weaker the polarity, and the higher the wall wettability are, the more unfavorable the adsorption of oil molecules on the wall is;③ In the combined wall, due to the influence of graphene wall, the adsorption amount of shale oil molecules increases with the increase of quartz wall wetting humidity. In addition, the adsorption transfer phenomenon of n-hexanoic acid and cyclohexane also occurs.