Abstract: In the hot dry rock geothermal mining, the evolution of granite fissures is very important for heat energy extraction.In order to explore the evolution law of granite fracture opening under cyclic high temperature, the seepage experiment of high-temperature single fracture granite with temperature of 100-300 ℃ is carried out by using multi-functional high-temperature triaxial servo control testing machine.The effects of different temperatures, temperature cycles (10 times) and seepage pressure on granite fracture opening are studied.The results show that no matter how high the temperature is, the fracture opening tends to increase with the increase of osmotic pressure, but the fracture opening increases with the increase of osmotic pressure at different temperatures, and there is an obvious turning point.When temperature is different, the turning point is different.No matter how high the osmotic pressure is, the fracture opening decreases with the increase of temperature, but the degree of decrease is related to the temperature.For the first few temperature cycles at the same osmotic pressure, no matter how high the cycle temperature is, the fracture opening decreases.When the number of cycles gradually increases, the fracture opening also increases.The higher the temperature, the more obvious the tendency of increase.The experimental results can provide basic experimental data for the in-depth study on controlling the evolution of granite fractures in the future.