Abstract: By using the analytical methods such as scanning electron microscope observation,low temperature liquid Nitrogen and CO₂ adsorption experiment and high pressure mercury injection experiment, this study conduct a comprehensively analysis on optimal pore segment of shale in Early Cambrian Niutitang Formation. The result shows that the Niutitang Formation is a good shale gas reservoir with well-developed pores and good connectivity. Micro-pores and nano-scale pores are developed well, and the pore forms are ink-bottle pores, conical pores and other amorphous pores, which provide large specific surface area for gas absorption. Organic matter pores, intergranular pores and intergranular pores are also developed with good connectivity, and most of the pore sizes are 100 nm~5 μm. Besides, macropores (>1 000 nm) has good connectivity, which is beneficial to gas desorption, diffusion and permeation.It has a higher pore volume and a larger specific surface area, providing a larger adsorption space for the gas.