Abstract: This paper aims to study the influence of high temperature on the physical-mechanical properties and acoustic emission characteristics of sandstone. It uses Brazilian splitting test on sandstone treated at 25~900℃. Meanwhile, it exames the changes in tensile strength, volume expansion ratio, mass loss ratio, P-wave velocity, macro and micro failure characteristics, acoustic emission characteristics and other properties in combination with scanning electron microscope(SEM) and acoustic emission(AE). The results show the following four findings. (1)After high temperature treatment, the mass, P-wave velocity, tensile strength and residual tensile strength of sandstone decrease to different degrees, and the volume also expands; (2)In the 200~400℃, the tensile strength decreases greatly, indicating that the threshold temperature of thermal damage is in this range; (3)The failure of sandstone is mainly caused by a single main crack, and the formation of secondary cracks is less and the brittleness of sandstone is more significant with the increase of temperature; (4)The results of SEM show that there are a large number of micro-cracks and micro-pores in the sandstone after the high-temperature treatment. The extension length, opening width, density, connectivity and extended range of the cracks are changed with the increase of temperature, leading to the decrease of mineral integrity; (5)AE characteristics of sandstone after heating are different, showing obvious characteristics of stage. Moreover, the AE activity become more stable with increasing temperature, and the peak value of AE events precedes the occurrence of sandstone failure, which can better monitor the failure of sandstone.