Abstract: Wells JY1 in the southeastern Sichuan Basin and TX1 in the southeastern Guizhou were used as examples for a systematic analysis of shale reservoir characteristics of the Wufeng-Longmaxi and Niutitang formations using mineralogy, organic geochemistry, pore structure, methane sorption, brittleness and fracture characteristics. (1) Organic pores with bigger pore sizes that could reach μm in the Longmaxi shale are well-developed in migrated organic matter rather than in in situ organic matter, which are the dominant reservoir spaces. However, organic pores in the Niutitang shale have lower amounts and sizes, commonly lower than 30 nm with more complicated pore structures. The inter-particle pores in the cataclastic organic-inorganic mineral masses are significant reservoir spaces and have stronger methane sorption and desorption capacities. (2) Due to the piecewise correlation between TOC content and brittleness, the developmental characteristics of pore and fracture have significant differences:when the TOC content is less than 6%, the TOC, brittleness, organic/inorganic pores and fractures had positive correlations; when the TOC content is greater than 6%, although the increase of ductility reduces the number of fractures, the lower cohesive strength, internal friction angle and more weak surfaces of interlayer fractures and cataclastic minerals favor to the development of slip fractures, which have significantly improved fracture effectiveness and reservoir space. (3) The Longmaxi, Wufeng and Niutitang shale respectively represent the characteristics of reservoir evolution under different geological conditions, i.e. with the thermal evolution, diagenesis and tectonic deformation and pressure relief, the size, scale and proportion of organic pores gradually decrease, the complexity of pore-fracture structure, methane sorption/desorption capacity and the proportion of inorganic pores and fractures in reservoir space gradually increase.