The purpose of this study is to estimate structural characteristic for air inlet part of ramjet in condition of flight at 12-15km height. Because air inlet part of ramjet is heated up to 700oK, high temperature properties such as Young’s modulus, thermal expansion coefficients and thermal conductivity coefficients are applied to the analysis. The analysis of transient temperature and thermal stress was performed by the finite element method with nonlinear code ABAQUS. The analysis was performed using several thermal coefficient and material properties to select preliminary design model for flight condition. Thermal boundary conditions were applied at ramjet inlet part until 0.01sec. The results of the analysis recommend tendency of thermal stress and temperature distribution. These are useful to select the structural material and to determine shape of air inlet part which satisfy the structural design safety.