Abstract: The dynamic compressive mechanical properties and impact fracture fractal characteristics of multi walled carbon nanotube (MWCNTs) reinforced concrete (MC) after high temperature were studied by split Hopkinson compression bar (SHPB). The relationship between the dynamic mechanical properties and fractal dimensions of MC was established, and the strengthening mechanism of MWCNTs on the dynamic mechanical properties of concrete was discussed. The results show that with the increase of temperature, the dynamic mechanical properties (dynamic strength, impact toughness and energy consumption) of MC decrease, and the impact crushing degree increases. However, at 200 ℃, the dynamic mechanical properties of MC increase compared with that at normal temperature. At the same temperature, the strain rate sensitivity and dynamic mechanical properties of MC are higher than those of plain concrete, while the impact crushing degree and fractal dimension are lower than those of plain concrete. The addition of MWCNTs effectively improves the high temperature resistance and impact resistance of concrete. The dynamic compressive strength, energy consumption and impact toughness of MC increase first and then decrease with the increase of fractal dimension after high temperature water cooling. In addition, the water-cooling mode also has a significant impact on the dynamic mechanical properties and impact fracture characteristics of MC. The properties of the spray-cooled specimen after high temperature are better than those of the quench-cooled specimen.