The pool-forming mechanism of coalbed methane has its own characteristics. In this paper, based on studies on the typical coal-bearing basins in China, it is pointed out that the reservoir formation of medium- to high-rank coalbed methane has experienced three critical stages: the coalbed methane generation and adsorption stage, the coalbed adsorption capacity enhancement stage, and the coalbed methane desorption-diffusion and preservation stage. The regional tectonic evolution, hydrodynamic conditions and sealing conditions play important roles in the stage of coalbed methane desorption-diffusion and preservation. Medium- to high-rank coalbed methane has three types of enrichment models, that is, the most favorable, the relatively favorable, and the unfavorable enrichment models.