In order to compare and analyze the on-site desorption performance and numerical simulation desorption performance of low coalification reservoir coal core, the on-site gas content of coal core of a coalbed methane (CBM) well in Xinjiang was measured, and a numerical model of coal core in undersaturated reservoir with adsorbed gas is established, and based on this, the loss gas content calculation method was analyzed. The results show that the loss gas, desorption gas and residual gas contents calculated by the desorption numerical model of the unsaturated coal core (adsorbed gas saturation 54.77%, 77.51%, and 99.79%, respectively) were close to the corresponding results measured in the field (error