Comprehending the temperature-dependent mechanical behaviour of reservoir rocks under cyclic heating and cooling conditions holds significant implications for various deep-earth engineering applications, namely deep geothermal energy recovery, deep nuclear waste disposal, and coal gasification. In this study, the thermo-mechanical behaviour of Australian Harcourt granite is examined through a cyclic heating and quenching process. A series of comprehensive experiments were conducted to analyse the stiffness of the material, across a range of temperatures (20 °C–900 °C) and quenching cycles (1–15 cycles). The fracture distribution resulting from quenching cycles was investigated using Micro-CT scanning, while acoustic emission technology was employed to examine the fracture development, propagation, and failure process during shearing. The findings revealed that as temperature and heating/cooling cycles increased, the compressive strength, Young's modulus, shear modulus, crack