This study is for figuring out a possibility of realization of the thermal protection system(TPS) for temporary use under high temperature condition and improving a design of the future TPS. On this purpose, environmental condition of the system has been simplified: the boundary conditions consist of a internally heating surface and a externally heated surface which is simulating the external high temperature condition. Configuration of the system is simplified as a hexahedon. Melting characteristics of the phase change material(PCM) and air temperature variation of TPS with or without connector have been numerically analyzed and compared. As a result of numerical analysis, the heat from the internally heated surface could not be effectively transferred. Therefore, temperature of inner space has been increased.