Abstract: The gas content of coal reservoir is the core parameter of coalbed methane production. There is an error between the measured gas content and the real gas content of coal reservoir. In this paper, based on the gas production of Haishiwan coalbed methane wells in different periods and the decrease of the "constant volume" of the gas content of coal reservoirs, the real-time gas content of coal reservoirs is inverted, and the change rule of the real-time gas content in the process of coalbed methane well drainage is explored. The results show that: (1) The gas content of coal reservoir decreases linearly with the drainage time t. the gas production of different long coalbed methane wells is consistent with the decrease of coal reservoir gas content, and follows the characteristics of "constant volume" gas production, that is, the gas production of single coalbed methane well is the "constant volume" production of coal matrix; (2) The gas production of coalbed methane wells has nothing to do with the original gas content of coal reservoir, but is related to the reduction of gas content; (3) The coal reservoir is a water-resistant layer, and hydraulic fracturing is difficult to change the combined water state of coal-based micropore channels. The CH₄ production process is controlled by the water-coal interface. Coalbed methane production is the result of mass transfer at the three-phase interface of "CH₄, coal and water", in which water turbulence provides and transfers energy to stimulate the desorption and production of CH₄ in block coal.