Abstract: The dynamic mechanical properties of red sandstone at negative temperature were studied by the dynamic impact test of Hopkinson pressure bar (SHPB), and the effects of different degrees of negative temperature on strength, damage variables and energy dissipation of rock were analyzed. Based on the microscopic fracture morphology obtained by SEM scanning, the reasons for the deterioration of dynamic mechanical properties of rock under low negative temperature were revealed. The study shows that low negative temperature will lead to frostbite of red sandstone, which will lose bearing capacity rapidly under high strain rate loading, and the dynamic mechanical strength will drop sharply; The negative temperature is equivalent to applying precompressive stress to the red sandstone, the whole rock tends to be brittle, but the ability to resist tensile stress is enhanced. According to the fracture morphology analysis, red sandstone appears strength degradation after -30℃.