Coalbed gas content is one of the basic parameter for predicting the risk of coal and gas outburst and evaluating mine gas reserve. In view of the shortcomings that the existing methods need to determine the gas content with the measurements at surface and underground and are timeconsuming，an underground integrated method for determining coalbed gas content is proposed. The composition and main technical indexes of key units such as coal sample underground direct crushing system，gas desorption automatic measurement system and data automatic collection and processing system are introduced. In terms of the large estimation error of gas loss in the existing methods and considering the heterogeneity of coal pore structure,a gas fractional diffusion model is established to accurately calculate the gas loss during coal exposure. An error analysis system simulating the underground coalbed gas content determination is established. The gas content is changed by setting different adsorption equilibrium pressures and different exposure times. The accuracy of the fractional model is verified by comparing it with the traditional model. The experiment shows that the error of calculating gas loss by fractional model is less than 10%，and the error of measuring gas content is less than 5%，while the error of measuring gas content by traditional model and power function model is more than 20%. Finally，based on underground integrated method of determining coalbed gas content，the CWH12 coalbed gas content meter is invented and applied in the Zhujidong and Pansan coal mines in the Huainan mining area. The traditional measurement equipment is used to measure gas content and compare with CWH12 for the coal samples at the same location and depth. The field test shows that compared with the original equipment，the measurement values of CWH12 is improved by 13.5% on average，and the measurement time is shortened to less than 1.5 h，realizing the rapid and accurate determination of coalbed gas content.