In view of the problem of low mechanical drilling speed in the hard rock such as granite and gneiss in the geothermal drilling at present， a mechanical rotary-percussive screw drilling tool is introduced and tested in granite formation of JHR-1 well and gneiss formation of HG-1 well. Compared with the ordinary screw drilling tool， the mechanical drilling speed of the rotary-percussive screw drilling tool increases respectively by 10%， 8.4% and 7.6% in ?215.9 mm well section of JHR-1， ?215.9 mm and ?311.2mm well section of HG-1， and no other side effects exist during the drilling process. The test proves that the mechanical drilling speed can be effectively improved by the use of rotary-percussive screw drilling tool， which provides a foundation for the application and popularization of the rotary-percussive screw drilling tool in the drilling of hard rock such as granite and gneiss.