Abstract: For the insufficient of gas extraction hole drilling technology in underground complex formation, we study the casing protecting hole screen pipe complete equipment. First, we improve the design of core detachable PDC bit to meet the trafficability requirements of screen pipe, design specification of φ40 mm screw thread screen pipe to case from inner hole of drilling by manual work with good connection reliability and convenient breakout; the developed solid tube device at bottom of the hole effectively solves the phenomenon that screen pipe is brought out when the drilling is raised, which ensures reliable, convenient and flexible assembly in installing screen pipe; compared with the traditional lifting drill and casing screen pipe technology, it has obvious technological advancement and casing efficiency is up by more than 2 times; the average depth of the casing tube is more than 91%, the drainage effect also shows that gas extraction concentration increased by 10% to 20 % after using the technology face.