This study is conducted in order to estimate the structural characteristics for inlet port of air breathing engine under flight condition at 12 ~ 15 km height and Mach Number 2 ~ 4. Inlet port of air breathing engine is heated up from 307 oC to 427 oC, so that is reached plastic zone partially. The material properties at high temperature such as young’s modulus, thermal expansion coefficients and thermal conductivity are applied to the analysis. The transient temperature and stress analysis are performed by the finite element method using nonlinear commercial code ABAQUS. The analysis is performed for the two materials, Titanium alloy and AISI4130 Steel and two FEM element type, shell and solid, to select preliminary design model for flight condition. Thermal boundary conditions are applied at inlet port until 5 s, and these conditions are maintained until 150 s. The results of the analysis recommend tendency of thermal stress and temperature contour. This study is expected useful to select the structural material and to determine shape of air inlet port of air breathing engine which satisfied the structural design safety.