Abstract: The characteristics of a CBM well performance is complex due to multiple influencing factors. It is beneficial for well site / layer selection and fracturing design to diagnose the performance of single CBM well. Based on the geolog- ical conditions and well performance data of 30 CBM wells producing from No. 3 coal seam of Permian Shanxi forma- tion in Shizhuang block,this paper studies the characteristics of CBM Wells performances and the relationship between gas production and water production. A negative enveloping relationship between gas production and water production is revealed,with high water production generally inhibiting high gas production. From a point of view of closeness of system borehole-stimulated coal interval,the mechanism of high water production due to outside water supply from sandstone aquifers is discussed and a hierarchical performance diagnostic method for single CBM well is proposed. The performance of some typical well are diagnosed using this hierarchical method,showing the method provides a tool for understanding the performance of single CBM well in Shizhuang CBM block and the application of this method can be extended to other CBM blocks.