Abstract: By comparing the quantitative pore results of geological samples from natural evolution profiles and simulated experiment samples, it is believed that the volume changes of pores of different scales are basically similar throughout the evolution of source rocks. Macropores and mesopores have a greater impact on pore changes. They should be the main contributors to the total porosity of rocks, and there is a certain conversion relationship between pores of different sizes. Diagenetic evolution and tectonic changes are the main external factors that cause pore changes while hydrocarbon generation and expulsion processes are the internal factors. In addition, there are some differences in the pore space and size (scale) of hydrocarbon products formed by source rocks during different evolutionary stages. This is useful for determining the storage mechanism of conventional and unconventional oil and gas resources corresponding to different evolutionary stages in the shale formation.