With the increase of mining depth and cost, gob-side entry retaining technology is widely used in thick coal seam mining, which reduces the mining cost and improves the recovery rate of coal resources. However, due to the pressure of the roof, the coal pillars on the side of the gob-side entry retaining are prone to cracks, resulting in serious hidden dangers of air leakage in the goaf. Therefore, this paper takes the 8521 working face of Chenjiagou Coal Mine as the research object, and uses the method of theoretical analysis, field air leakage test and numerical simulation to analyze the distribution characteristics of air leakage channels in goaf of gob-side entry retaining under W-type ventilation mode, and grasps the evolution law of key air leakage areas. The results show that the main air leakage channel is 1 ~ 3 # flexible formwork wall when the fully mechanized caving face of gob-side entry retaining is advanced to 54 m, and the range of air leakage flow field is 5.57 m / min-71.46 m / min. When the working face advances to 126 m, the main air leakage channel is 3 ~ 18 # flexible formwork wall, and the range of air leakage flow field is 4.11 m / min-52.90 m / min. The air leakage rate decreases gradually in the range of 0 ~ 80 m along the strike direction in the deep part of the goaf. In the range of 20 m in the shallow part of the goaf, the overall air leakage rate is exponentially related to the distance from the working face. The research results can provide theoretical guidance for the prevention and control of coal spontaneous combustion in gob-side entry retaining.