To study the influence of pore structure on shale oil accumulation, the pore structures of shales from Qingshankou Formation in Songliao Basin were determined by the mercury intrusion capillary pressure (MICP) method and the pore-throat ratio was calculated according to ink-bottle pore model. The results show that the porosity of these shales vary from 5. 0% to 8. 0%, the average pore size and pore-throat ratio are in a range of 7. 2-13. 5 nm and 4. 9-36. 2, respectively. The Hg-retained ratio is between 61% and 84%, indicating the poor connectivity of shale pores. The shales are dominated by nanoscale pores, and contain a small amount of micronscale pores. The nanoscale pores show a smaller value of pore-throat ratio and have a relatively good pore connectivity, while the micronscale pores display a larger value of pore-throat ratio and have a relatively poor pore connectivity. It is considered that the micronscale pores could be considered as the primarily store space of shale oil and the nanoscale pores act as the major pore-throats for shale oil accumulation. <摘要译文>