Abstract: Coal mine gas extraction system is a comprehensive system affecting coal seam gas extraction and guaranteeing safety in production of coal mine. In this paper, the theory of graph and resistance loss is regarded as guidelines, and the online data of monitoring system for mine gas extraction is used as the basis of calculation, the frictional resistance of high negative pressure extraction system about M18 coal seam of Weishe Coal Mine is calculated and analyzed, and 3 key branches which have the maximum resistance loss of pipeline are found. Finally, extraction pipeline network is optimized based on the method of pipeline diameter optimization, the extraction effect is improved and extraction energy is reduced, which obtains very good effect of field application.