Two structures of metallic thermal protection system(TPS) for hypersonic vehicle were presented. One model was a multi-layer construction and the other has cavities in the metallic layer. Numerical simulations were conducted on the three-dimensional TPS models using CFD software of Gambit and Fluent. Two heating temperatures of 1073K and 773K with constant temperature and isothermal boundary conditions were considered. Heat transfer was treated as single conductivity and thermal radiation effect was not involved. The results of simulation investigation showed that: The metallic layer had poor capability to restrict the heat conductivity. Heat was easier to transfer across the bracket into the internal part of the TPS. The ability of cavities in metallic layer to resist heat conductivity was limited. The temperature-heating time variation pattern was similar for different external heating temperature. Internal cooling was important for the TPS. The thermal radiation effect on the TPS would be focused in further research.