Hydraulic fracturing technique, which is widely used to enhance the permeability of tight geological formations, has been employed to stimulate unconventional geothermal systems. However, these reservoirs are accompanied by high in-situ stresses and large geothermal gradients. Therefore, it is important to understand the hydraulic fracturing process and the respective permeability enhancement under extreme temperature and pressure conditions. Therefore, the aim of the present study is to understand the effect of flow performance of hydraulically fractured granite under high temperature and pressure conditions. A series of flow-through experiments were conducted on granite specimens which were hydraulically fractured under 60 MPa confining pressure and two temperature conditions: room temperature and 300 °C. Corresponding influence on rock microstructure was studied using high- resolution CT imaging with the IMBL facility of Australian Synchrotron. Based on the experimental results, it was found that one single fracture is induced at room temperature. However, a perforated zone with multiple inter-crystalline cracks is induced in the wellbore zone under the high-temperature fracturing process. Therefore, the measured permeability was almost one order higher in the sample hydraulically fractured under high temperature up to 20 MPa confining pressure. Further, it was identified that the fracture permeability and the fluid discharge were strongly stressed dependent.