Abstract: Based on the elasticity theory and analyzing the characteristics of stress distribution near the cavity-completed wells, the paper establishes the limit equilibrium equation, then deduces the "R" which says the distance between the sidewall of the cavity-completed wells and the peak stress. The relation between the stress-concentrated zone caused by cavity-completed wells and the coal powder output is concluded by means of the theory of mechanics of materials and the statistical observations of construction records, the conclusions are as follows:the relationship is positive between the output amount of coal powder and the distance of the peak stress caused by cavity-completed wells if there is not big difference in conditions of the geological environment and the CBM geological parameters. The conclusion confirms that the coal powder may be produced if the original stress state changes. It has certain practical significance to CBM industrial production.