Abstract: Starting from the requirements of gas sub-source identification in working face, combining with the existing regulations of gas sensor installation in mining face, the paper presents that the gas emission of dropping coal is relatively easy to be extracted from the total gas flow in the return airway. Combined with the actual situation of 11010 working face in a coal mine, using Fluent fluid analysis software, the mixing process of dropping coal gas and air flow in this working face is simulated and analyzed. Based on the simulation of the different wind speed of the working face, the distance between the dropping coal gas and the wind is inversely proportional to the inlet wind speed. Combined with the actual wind speed value of working face, the paper simulated the actual air flow condition at cross section with the horizontal distance of 5 m, 10 m, 15 m and 30 m respectively in return airway. According to the ratio of the mean wind velocity in the symmetrical region, the mixing degree of gas flow and air flow is measured.