Abstract: For the problems of difficult construction in downward holes and ineffective gas extraction caused by the sufficient water storage in No.4 coal seam roof and floor of Gubei Coal Mine, we study downward holes under the condition of high riched water, including hole forming, hole protecting, hole sealing and drainage. The results showed that the average flow of single-hole of 5^# drilling field with grouting waterproof and drainage measure is almost double that of 2-3^# drilling field. The average concentration of single-hole of 5^# drilling field were taken is 10 times as much as 2-3^# drilling field and it is still 4 times as much as 2-3^# drilling field after 14 days of extraction. Grouting and drainage measures obviously improved the efficiency of the downward holes gas extraction.