Abstract: To make clear pore structures and flow characteristics of shale oil reservoir, taking the shale oil reservoir of Permian Lucaogou formation in Jimsar sag as the study object, the paper uses Micro-CT and FIB-SEM scanning technologies to establish a 3D digital core model and to obtain parameters of pore throat structures. Based on which a microscale physical simulation instrument for porous media is established to study the low-velocity flow laws of fluids in micro paths. Meanwhile, the physical simulation model is used to measure flow characteristics and damage degree of different fracturing fluids. The study results show that the pore structure of the shale oil reservoir is featured with strong heterogeneity and poor connectivity, the main reservoir space is dominated by nanoscale pores and the fluidity depends on the amount and sizes of the micron-scale pores; the low-velocity flow of fluid at micro scale is non-darcy flow with a threshold pressure gradient, and with the increase of driving differential pressure, the fluid in more pores will continue to flow; the residue of guar gel breaker and the aggregates of macromolecular structure are easy to block pores. It is suggested that less guar gel and more slick water should be used to reduce reservoir damage during shale oil reservoir fracturing