The apparent characteristics, mass loss and mechanical properties of Ultra-High Performance Concrete after exposure to high temperature were studied through the high temperature heating test and the cubic compressive strength test of Ultra-High Performance Concrete. The effects of steel fiber, polypropylene fiber, steel fiber and polypropylene fiber on cracking suppression of Ultra-High Performance Concrete were compared. The effects of temperature, fiber type and content, aggregate (quartz sand and steel slag) on the strength of Ultra-High Performance Concrete were investigated. The test results show that 2% steel fibers and 1% polypropylene fibers can effectively restrain high temperature explosion behavior, and the specimen remains intact after high temperature. Ultra-High Performance Concrete with steel slag aggregate and hybrid fiber has excellent high temperature mechanical properties, the residual strength of 67% can still be maintained after being exposed to high temperature at 1000℃. With the increase of temperature, the cubic compressive strength of Ultra-High Performance Concrete increases first and then decreases. High temperature enhances the compressive ductility of Ultra-High Performance Concrete when the target temperature is more than 600℃.