Abstract: In order to obtain the dynamic eqilibrium relationship among pressure, gas and water production in coalbed methane well drainage of high rank coal res ervoir, and reveal coalbed methane drainage effect as well as its mechanism under pressure control, taking X1 well and X2 well in southern Qinshui basin as examples, and based on drainage stages classification of X1 well, fluid effect and desorption laws in the two coalbed methane wells drainage were analyzed under changing press ure, relationships among gas production and casing pressure, dynamic liquid level height, pressure of downhose, depletion pressure were discussed and researched, a nd the variation characteristics of gas production before and after pressure control of X2 well were numerically simulated. The results showed that fluid effect in coalbed methane wells depend on control of casing pressure in the initial stage of drainage, a shutoff pressure and controlling pressure production system could contribute to co albed methane well productivity effectively.