Abstract: In this paper it measured the amount of air leakage in 4405 goaf of Hongyan Coal Mine through the SF₆ tracer gas, and determined the major air leakage direction. On this basis it optimized the nitrogen injection process in 4405 goaf, which made the analysis of nitrogen injection more accurate and reliable. It was essential to determine the size and direction of air leakage in goaf, which affected nitrogen injection, thus ensured safe mining in the coalface.