Thermoelectric generator (TEG) can utilize intermittent temperature fluctuations of the aircraft's fuselage to provide power for wireless structural health monitoring systems. In this article, a novel phase change material (PCM)-TEG system of integrating PCM with TEG for improving the output performance was reported. The proposed system was almost adiabatic with the external environment, which effectively avoided heat exchange with the internal environment of the aircraft. High-performance paraffin/expanded graphite (EG) composite PCM was fabricated by a simple melting-adsorption approach.Because of the porous structure and high thermal conductivity of EG, significant enhancement in the thermal conductivity of the composite was observed, while there was little decrease in the latent heat capacity. A variety of typical experimental conditions were designed by aero-thermal calculation method that based on the actual service environment of aircraft. The output performance of the TEG and thermal transfer properties of the composite were investigated systematically, which showed that the existence of PCM increased the temperature difference between the two sides of the TEG and effectively promoted its energy conversion potential. Finally, the performance for the PCM-TEG system was also compared under different experimental conditions. The study provides a solution for obtaining electrical power source, which is highly desired in wireless structural health monitoring systems.