In order to quantify the degree of rock damage caused by high temperature,the Fangshan marble under high temperature was used to explore the degree of rock thermal damage and evolution process from the basic physical parameters,mesostructure and microstructure.First,samples were treated at eight temperatures within the range of 25~850 ℃.Then,the microstructure evolution of rock with temperature was obtained through CT scanning technology and SEM test.The coefficient of phase variation proposed in this paper,combined with microscopic characteristics of marble after heating,wave velocity,density and CT value described the thermal damage.The results show that the four indexes embody different sensitivity with the change of uniaxial compressive strength at different temperature stages.Among them,the wave velocity response is the most obvious in the range of 25~250 ℃;at 250~450 ℃,the CT value can best reflect the change of thermal damage;at 450~700 ℃,the coefficient of phase variation is the most sensitive to the degree of damage.Based on the results,the uniaxial compressive strength prediction formula of rock treated by high temperature containing damage index is established in sections.The uniaxial compressive strength can be predicted based on some sensitive factors,which has some reference for the excavation of rock mass and the design of supporting structure in deep underground engineering.