Abstract: According to the problem of hydraulic punching in Mengjin Coal Mine, west of Henan province, it analyzed in detail from hydraulics theory, drilling layout and punching process. Through changing the multi-nozzle to the equivalent nozzle, it calculated the pressure of water jet determined by equivalent diameter and flow coefficient. It put forward the synclastic effect and reverse effect between water jet pressure and gas pressure. Through selecting the effective punching tools, it optimized boreholes arrangement, and it realized rapid outburst elimination in the coal seam of poor permeability by using the two times punching process of first under and second upper. The site investigation showed that the measure could eliminate the outburst danger effectively, the driving speed of protection roadway increased from 35m/month to 115 m/month, it achieved good results.