Aiming at the problem of air leakage in the goaf of high gas unicom in fully mechanized caving face, the tracer gas method is used to detect the air leakage channel. Through theoretical analysis of the air leakage mechanism, the SF6 gas is released on site and the concentration change is detected to determine the source and intensity of air leakage. The results show that there is air leakage in the adjacent goaf between the air inlet and the goaf, and the air leakage in the return air trough is not obvious. The research results provide data support for the formulation of fire prevention and extinguishing measures in fully mechanized caving face.