Abstract: The thermo-cracking of granite will happen under high temperature and high pressure. Its intensity and fracture toughness both decrease. Study on the percussive rotary drilling law under various temperatures is of great significance because it can provide a theoretical basis for new drilling process designed for geothermal production. The law of impact grinding through experiments on a large-size (f 200 mm × 400 mm) granite is studied by use of the 20 MN servo-controlled triaxial rock testing machine with high temperature and pressure. The conclusions are as follows: (1) under high pressure, the intensity of granite gradually decreases and the percussive rotary drilling speed increases gradually with the increase of temperature; (2) under high pressure, the unit energy consumption for percussive rotary drilling decreases and the drilling efficiency is greatly improved with the increase of temperature; (3) under high temperature and high pressure and within some drilling pressure and percussive power limit, the drilling speed increases with the increase of pressure or power. The unit rock-crashing power consumption gradually decreases with the increase of pressure.