Abstract: This paper studies the phenomenon of huge difference in production capacity of six adjacent CBM vertical wells in Zhengzhuang block under the condition that the geological factors and engineering factors are basically the same. Affecting factors of CBM wells, such as burial depth, gas content, coal seam thickness, geological structure, fracturing engineering and drainage engineering, are analyzed in detail. It is believed that low permeability of coal reservoir is the controlling factor of low production of CBM vertical wells in Zhengzhuang area. The mechanism of formation is due to the formation and density of structural fissures in coal reservoirs controlled by paleogeostress field, they do not match with the degree of fracture opening in coal reservoirs controlled by present geostress field, which determines the heterogeneity of low permeability of coal reservoirs in Zhengzhuang block.