Abstract: An engineering method for sizing the thermal protection system(TPS) of hypersonic vehicles was built.Complex optimization method was used to seek optimal thickness with the aim to minimize the TPS weight and limit the aircraft main-structure temperature under acceptable bound.A general purpose finite element(FE) analysis tool NASTRAN was used to get time-variable temperature field at given TPS size.An interface code was created to relate and combine the FE thermal analysis and optimization solving.Details of data exchange between them are present.Finally a numerical example was given and optimization results were discussed detailed.