Shale oil is an important part of unconventional energy and has become a new trend of global unconventional oil and gas exploration and development. The development of shale oil requires large-scale hydraulic fracturing technology, and clarifying the seepage law within the shale porous medium of the huff and puff process is of great significance for improving shale oil recovery. Based on the scanning electron microscope images of Jiyang shale, the structure of shale porous medium containing multi-scale pore and fracture space is constructed. Subsequently, a multicomponent multiphase Shan-Chen lattice Boltzmann model is adopted, and the constructed model is validated using the classical cases of Laplace's law and contact angle models. Then, the simulation of huff and puff process in shale porous media was carried out, and the effects of injection pressure difference, soaking time and producing rate were analyzed. The results show that increasing the injection differential pressure can help to achieve better development results; the fracturing fluid can enter the fracture seam and displace the oil phase inside during the soaking stage, and the fracturing fluid return rate tends to decrease with the increase of the soaking time; the water-wetted cores have better development results than the neutral and oil-wetted cores; and the higher fluid discharge rate will cause the pressure inside the pore to drop rapidly, which is not conducive to the development and production of shale oil in the following period. In this paper, the fluid flow mechanism during the shale oil huff and puff process is investigated from the perspective of pore-scale simulation, which provides support for the formulation of a reasonable production work schedule of shale oil wells.