At present， the depth of sedimentary rock geothermal drilling using air down-the-hole hammer technology is mostly about 1000m. The greater the formation depth， the more difficult it is to drill with air down-the-hole hammer. A geothermal well in Kangping， Liaoning Province， was drilled using air down-the-hole hammer technology to achieve a breakthrough in the depth of geothermal wells in sedimentary rocks， with a drilling depth of 2250m. Air drilling technology is adopted for the construction of the whole well， and proper working air pressure and air volume are selected to promote the popularization and application of this technology in deep geothermal wells in sedimentary rocks.