Abstract: In order to understand the fluid output characteristics of the CBM well in Xishan Area,Shanxi Province,the gas production rate,water production rate,and casing pressure variations in different production stages were analyzed respectively.The results show that the gas production rate of CBM wells in Xishan Area is relatively low,and the period of stable gas production stage is short which causes the early coming of declining gas production stage.The geological factors and the engineering factors about the low production of CBM wells are analyzed respectively,and it is found that the geological factors include coalbody structure,gas content,permeability and hydrogeological conditions.In view of drainage Engineering,the meaning of casing pressure threshold is proposed and its influences on gas production is studied.It is thought that when the declining rate of casing pressure is 0.000 9～0.002 1 MPa/d and the casing pressure is kept above 0.33 MPa during CBM production,the gas production can be stable and continuous.