Mining protective layer, pre-extraction coal seam gas enables to eliminate outburst risk, pre-drainage gas outburst technology was adopted without protective layer mining, No. 2 coal seam with low air permeability, difficult drilling construction, low drainage rate, became the safe hazard. In order to eliminate the outburst an danger and improve the drainage rate, hydraulic piercing technology was adopted to increase gas permeability, releasing the gas in the coal body and clearing the outburst danger. The test showed that single hole coal injection 1.2 ~ 4 t/m, the average amount of gas extraction in a single hole increased by 4.68 times after punching, bore diameter 94 mm extraction time of the extraction hole reached 15 d, radius of influence 8 m, pre-drainage radius increased two times pre-drainage time 75 d.