In order to study the difference between the initial gas emission curves of single property and composite coal seam drilling, Comsol Multiphysics was used to simulate the initial gas emission curve of drilling process, and the initial gas emission data of three groups of drilling were monitored by the coal seam simulation device and the continuous flow method. The variation law of gas emission with drilling depth in the drilling process of different coal seams was demonstrated. The research shows that the instantaneous velocity of gas in the fracture zone is 19 times that of the normal, and the gas in the borehole is concentrated in the front of the drill pipe, and the emission rate decreases rapidly after 2 s of exposure. However, there is an obvious monotonically increasing function relationship between the overall drilling distance and the initial gas emission curve of the borehole, and the growth rate gradually slows down with time, which is also verified in the subsequent experiments in Haizi and Weixu coal mines. The initial gas emission of borehole in composite coal seam ( hard coal contains soft coal ) was measured by HSBC coal sample. The change trend of initial gas emission in abnormal area of gas curve is similar to that of numerical simulation, and the peak value of abnormal area is 3.8 times higher than normal value, indicating that the parameter is sensitive to composite coal seam.