The increase of deep underground works has led to many concerns in relation to the dynamic characteristics of rocks subject to heating treatment, including underground rock blasting. For revelation of the dynamic mechanical properties of rocks subject to heating treatment, the sandstone treated after 22°C, 150°C, 300°C, 450°C, 600°C, and 750°C respectively were subject to dynamic fracture toughness tests using Split Hopkinson Pressure Bar (SHPB). After reaching the set temperature, it is maintained for 30 min and then cooled for 24 h to normal temperature. the morphology of microcracks on the surface of sandstone samples due to thermodynamic action was observed by electron microscope scanning (sem). The P wave velocity of rock samples after high temperature is measured, and the results can be correlated with scanning electron microscope images. Finally, the relationship between temperature and dynamic fracture toughness is analyzed. Results showed: when the loading rate was lower (<50GPa•m<sup>1/2</sup>s<sup>-1</sup>), the fracture toughness values corresponding to different temperatures of heat treatment tended to be closer with each other. However, when the loading rate was higher, the fracture toughness values varied greatly. Under certain special loading rates that are the same, the fracture toughness of sandstone at 300°C is about 6% higher than at 150°C. This can be attributed that the expansion of minerals at high temperature results in the closure of original cracks in the rocks, the change in internal structure of rocks, and the increased fracture toughness.