Abstract: Based on the single-well analysis and appraisal, the Ar-ion milling/SEM technology is used to study the porous type of Longmaxi Formation in Pengshui area of southeastern Sichuan Basin. The pores of shale in the study block are divided into six types (including microfractures, intergranular pores, intercrystalline pores, intragranular pores, organic matter pores and biological fossil inner pores). The nitrogen adsorption and mercury intrusion methods are used to inspect pore sizes and its distribution. Distribution of pore sizes is normalized to obtain the continuous distribution of shale pores of the target formation. Namely the pores of 2 to 10nm size developed most. The five influencing factors of shale pore structure of Longmaxi Formation in the study block is brought under analysis and discussion – content of brittle minerals, content of clay minerals, TOC, diagenesis, and conservation conditions. The results of analysis show that TOC is the dominant intrinsic factor of the shale pore structure of Longmaxi Formation in Pengshui area.