Abstract: Shale pore structure is an important indicator that reflects its oil and gas storage capacity, flow capacity, and occurrence state. To investigate the pore structure characteristics of typical shales in the Sichuan Basin and the Ordos Basin, shale samples from the Longmaxi Formation in the Shizhu and Pengshui areas of Chongqing and the Chang 7 oil shale of the Yanchang Formation in the Yijun area of Shaanxi Province were collected, respectively. The pore structure characteristics of these three groups of shales were examined by mercury intrusion porosimetry and nitrogen adsorption tests. The irregularity and complexity of large pores(mesopores+macropores) and micropores were deeply investigated using the FHH model and the Brooks-Corey model. The results show that: (1)the pore morphology of the shales belongs to ink bottle shape and parallel plate slit shape; (2)the pore size distribution is multimodal. For the shale of the Longmaxi Formation, it contains micropores, mesopores, and macropores, while for the shale of the Yanchang Formation, most of the pores belong to mesopores and macropores; (3)compared with the shale of the Longmaxi Formation, the shale of the Yanchang Formation has lower porosity, pore volume, and fractal dimension. Therefore, the shale in this area possesses a simpler pore structure and a more compacted skeleton.