Abstract: By use of the 20 MN servo-controlled triaxial rock testing machine with high temperature and high pressure in China University of Mining and Technology, experimental study is carried out on the creep properties of large size granite specimens of Φ200 mm×400 mm under high temperature. The creep test methods and results of granite under a three-dimensional stress and high temperature are described. Based on the theory and the analysis of test results, it is discovered that granite experiences the first and second phases of creep at 300 ℃, axial stress of 94 MPa and lateral stress of 75 MPa. At the same time the creep deformation of granite shows clearly the characteristics of the steady-state creep and gradually stops. But at 400 ℃, axial stress of 94 MPa and lateral stress of 75 MPa, the deformation shows obvious characteristics of the non-steady-state creep. The research reveals that the creep properties of granite increase with the increase of temperature and stress. There is a threshold of temperature about transition from the steady-state creep at 300℃ to the non-steady-state creep at 400℃. Data obtained from experiments are of important guiding significance for the long-term security of nuclear waste disposal in the deep granite and long-term exploitation of geothermal energy.