Abstract: In order to solve the problems of serious collapse of long-distance directional drilling holes,low concentration of gas extraction and low flow rate in the roof of Liyazhuang Coal Mine under complex geological conditions,According to the construction technology of high directional long borehole and gas drainage principle of coal seam roof,the technology of screen pipe protection under full borehole of directional long borehole in roof under complex geological conditions is studied.The integrated technology of "drilling-back drilling-small diameter through hole-large diameter reaming-back drilling-down sieve tube in hole-back drilling" has been formed,the related technical equipment and engineering practice are also introduced.Field application of typical complex Geological conditions roof in Liyazhuang Coal Mine shows that:through this technology,the screen can be quickly lowered to the full hole section under complex geological conditions,the depth of the screen is up to 459 meters,and the average gas extraction concentration and pure extraction quantity can be increased by about 5 times and 10 times respectively.

Key words: Complex geological, Hole collapse, Reaming without retreating, Quick down sieve tube without retreating drilling holes, Gas extraction