Abstract: The triaxial compression mechanical properties of granite under the action of temperature from 25℃ to 1000℃ are investigated by means of the MTS815 hydraulic pressure servo material experiment system. By use of a D8 ADVANCE X-ray diffractometer, X-ray powder diffraction analysis on heated granite is also made. The results show that: (1) The relationship among triaxial compressive strength, axial peak strain of granite and confining pressure after high temperatures is nonlinear quadratic polynomial growth. The failure strain energy of rock samples increases with the increase of the confining pressure significantly, that is, they exhibit a linear relationship. (2) The triaxial compressive strength and failure strain energy of rock samples show a parabola relationship with temperature, with the maximum value being 400℃. (3) Three maximum diffraction intensities of quartz, feldspar and mica increase as the temperature increases before 400℃, then decrease with increasing temperature, and reach the maximum value at 400℃. (4) For the quartz, reversible reaction from quartz into quartz at 573℃ occurs. The differential thermal curve of feldspar shows endothermic valley at 700℃ ~ 900℃, and the structure changes from crystalline phase to amorphous phase. At 997℃, the mineral lattice of mica is damaged, the hydroxy escapes and albite forms. The mechanical properties of rock samples gradually deteriorate as the temperature rises after 400℃ because of the above factors.