Abstract: At present, most of the existing positioning methods of underground gas extraction main pipeline leakage in coal mines use single positioning method. The problems of these methods include poor applicability, low efficiency and susceptibility to environmental impact. In order to solve the above issues, this paper proposes a leakage positioning method of underground gas extraction main pipeline based on transient model by combining flow balance method, negative pressure wave method and wavelet noise reduction principle. Firstly, the method analyzes the flow change law and the difference of the both ends of of the pipeline, eliminate the interference signal, use the flow balance method to identify the pipeline leakage state and determine whether the pipeline is leaking. The method compares the flow changes under normal operation and leakage. When the difference between the both ends of the pipeline flow is greater than the threshold value of the pipeline flow difference, it means that the working conditions have changed or leakage occurs. Secondly, according to the propagation mechanism of negative pressure waves in the pipeline, wavelet noise reduction technique is used to denoise the pressure signal. The neighborhood interpolation method is applied to seek the signal mutation point. Finally, the leak location formula is used to calculate the leak position so as to obtain the leak position of the pipeline effectively. The simulation analysis results verify the accuracy of the method.