Abstract: In this article, the air leakage in goaf of the workface by U-type ventilation of the coal mine of Wenzhuang was tested by SF6 tracer gas technology. The results of tests showed that there were few channels of air leakage. The air leakage ratio of the goaf was 16.31% and the air leakage viscosity was from 0.032 m/s to 0.128 m/s. The results of numerical simulation show that the air leakage paths of the goaf with U-type ventilation were U-shaped. The air flowed in from the intake side of the workface and went out from the return side. Spontaneous combustion is more likely to occur in the upper part of the goaf in the roadway area of the working face. The three zones of goaf distribute in bar shape. The range of the three zones changed with the height. The area of oxidation zone increased first and then decreased with height and the area of heat dissipation zone gradually disappeared when the height was higher than 16.3m.