Abstract: The topography conditions of Chahasu Coal Mine belong to the gully area, the 3-1 coal seam has the feature of easy spontaneous. During the mining in No.3101 working face, the linked roadway sealing walls are damaged with a certain degree because of the strong mining pressure. Meanwhile, there are some large fractures on the surface produced by mining, and there is a serious air leakage hazard of sealing area and surface in the gob, which has the threat for safe mining in working face. The pressure differences between linked roadway sealing walls are measured in working face, and the air leakage ratio of the gob is obtained according to the test results. The tracer gas SF₆ is used to find the air leakage on the surface and the maximum velocity of air leakage in surface fracture is calculated. The reasons of air leakage are analyzed. Finally, several measures are taken to reduce air leakage and prevent coal spontaneous combustion effectively in gob, such as reducing air quantity and pressure, improving the quality of sealing walls, filling the surface fractures, etc.