In flight condition, the calculation of convective heat transfer coefficient should consider the influence of gas compressibility and heat exchange. Under flight conditions, the gas compressibility and heat exchange should be considered in the calculation of external convective heat transfer coefficient of aircraft. At present, the reference temperature method commonly used in engineering that ignores the influence of aircraft structure, and regards the external convective heat transfer coefficient of each part of the aircraft as a numerical value, which is bound to seriously affect the accuracy of calculation results. Based on the study of calculation principle of external convective heat transfer coefficient of civil aircraft, this paper proposes a simulation calculation method, that is limit temperature difference method, which can be used to solve the external convective heat transfer coefficient of each part of aircraft under flight conditions. STARCCM+software is used as the calculation platform to analyze the feasibility of a civil aircraft from the perspective of simulation calculation. Theoretical reference temperature method and heat transfer formula method are used to verify the accuracy of the calculation results of limit temperature difference method. The results show that the simulated values obtained by heat transfer formula method and limit temperature difference method are basically the same, and the difference between the different simulated values and the theoretical value of reference temperature method is about 8% of the theoretical values, so the results calculated by limit temperature difference method are in good agreement with the theoretical values.