Research of the coalbed methane (CBM) desorption can be used to predict gas production and gas continued period. The adsorption and desorption experiments for the coals are made in some active CBM exploration and development regions. Through the analysis of experimental data, the pressure-reduced desorption formula for the CBM follows . Calculates the CBM desorption quantity with the formula during the well drainage process. It reveals that the lag of pressure reducing desorption is due to the presence of residual gas content c，the desorption quantity ad and the maximum gas content amax show a linear correlation，the maximum desorption rate is c/amax，and improves the desorption in the production only by changing the heat of adsorption and the desorption rate. It is verified through the drainage practice of two vertical wells and two horizontal wells.