Abstract: To solve the problem that drilling in coal seam for gas drainage in Huangling mining No.2 Mine is easy to drill the roof and the floor of coal seam through, and cause drainage in blank zone and repeated cross, as well as small drainage area and short drainage time, this makes the gas control in advance impossible. Based on that, the gas drainage trial by directional long boreholes was carried out in medium-thick coal seam at No.409 working face in No.2 Mine. Through long drilling design and construction technology improvement, effectively improve the efficiency of construction. Two years after drainage, coal seam gas content is reduced to 1.56~1.73m3/t, drainage rate reached 42.52%~48.17%. The gas pressure of Coal seam reduced from 0.65 MPa to 0.19~0.28MPa.Time limit for the project was shorten 35 days, the initial flow of drilling gas was increased 1.46 times and total cost was saved 264600 yuan. Thus, effectively eliminated the coal extraction blind area and eliminated the gas overrun occur in the process of mining.