Fire was one of the most frequent and common major threats to public safety and social development. The mechanical properties of concrete would be significantly reduced when the high temperature of the fire continued for a long enough time. The introduction of nano-SiO2 could improve the performance of concrete. This paper mainly studied the mechanical properties of nano-SiO2 concrete at room temperature and high temperature. When the specimen was heated at a high temperature of 1000 °C, the surface of the concrete turns pale yellow. And there were small cracks and local explosions. The compressive strength of concrete increased with the concentration of nano-SiO2. And the higher the concentration of nano-SiO2, the higher the residual compressive strength was still after heating at a high temperature of 1000 ℃. After 1 and 2% nano-SiO2 were added, the microstructure of the matrix was significantly improved. And no Ca(OH)2 crystals were found. At the same time, it can be observed that the interfacial transition zone of aggregate and matrix was the weak link in the mechanical properties of concrete.