The storage space of shale reservoirs is mainly composed of nanoscale pores，in which the shale oil occurrence can have important influence on its flow law. The full-scale pore size distribution of shale pore structure and the main-frequency pore diameter of nanoscale pores in Dongying Depression were obtained by the nuclear magnetic resonance freezethaw（NMRF）technology. With the well effluent composition of Well NX55 in Dongying Depression，the molecular dynamics simulation was used to establish a typical nanoscale pore model of Dongying Depression，with which the occurrence of shale oil in nanoscale pores of organic matter was studied. The study results show as follow：①The main-frequency pore diameter of nanoscale pores in shale reservoirs of Dongying Depression is 15 nm；②The density of crude oil in the organic nanoscale pores gradually decreases from surface to center；③The shale oil molecules can form a“quasi-solid”layer on the walls of organic nanoscale pores，and its density is about 1.1-3.15 times that of the free crude oil in the center of the pores；④The shale oil molecules are adsorbed in four layers in organic nanoscale pores. The thickness of the first layer is the largest，and the calculated proportion of absorbed shale oil in Dongying Depression is 19.8%.