The pore evolution of organic- rich shale is closely related to the occurrence and enrichment of shale gas. It is of great significance to study the characteristics of pore connectivity and shape evolution for fine characterization of reservoir space and revealing the occurrence mechanism of shale gas. The low mature shale rich in organic matter in the Huangxian Formation of Paleogene was selected in this paper, and thermal simulation physical experiments were carried out to obtain simulation products with different thermal evolution degrees. Low temperature liquid nitrogen adsorption and scanning electron microscope experiments were undertaken, and digital image processing was carried out to extract pores, and the evolution characteristics of pore connectivity and shape coefficient were studied. The results show that: ① During the low mature stage, a small amount of organic pores developed, while inorganic pores were mainly mineral matrix pores. Along with the increase of thermal evolution, a large number of nearly circular organic pores are gradually formed, and a small number of dissolution pores and clay mineral interlayer pores are formed. At the over- mature stage, some pores are reduced or disappeared due to compaction. ② With the increase of thermal evolution degree, the pore diameters of both organic and inorganic pores increase at first and then decrease, and the pore shape coefficients all show a nearly V- shaped change trend. ③ High temperature and high pressure causes the peak value of the second dominant pore diameter of the sample pore system to become larger, which indicates that the narrow- slit pores are added in the pore system, which is helpful to communicate with other types of pores and improve the connectivity of the pore system. ④ A large number of nearly circular organic pores generated during thermal evolution can provide more adsorption sites for methane, and slit inorganic pores such as interlayer pores of clay minerals can improve pore connectivity, thus helping to improve the occurrence and migration capacity of shale gas. The research can provide a basis for shale gas reservoir characterization and shale gas occurrence and enrichment research.