With the continuous advancement of aerospace engine technology, prolonged operational durations have led to increasingly severe thermal environments for engine nozzles and adjacent electronic components. To ensure reliable functionality of these components under extreme temperatures, this study investigates the thermal management of the nozzle through integrated internal flow field analysis and heat transfer simulations. A finite element heat transfer model was established to evaluate the temperature distribution on the nozzle’s outer surface, enabling the design and optimization of an external thermal protection system (TPS). Key factors influencing the temperature field including thermophysical properties, geometric parameters, and radiative characteristics were systematically analyzed. Numerical results demonstrated a significant reduction in the front surface temperature of electronic components from 267.1 to 92.3 °C, achieving a total temperature drop of approximately 175 °C. Experimental validation confirmed the effectiveness of the proposed design, with a maximum measured temperature of 97.9 °C at the component surface, yielding a deviation of 6% from simulation results. This study offers a practical and scalable solution for enhancing the reliability and performance of aerospace engine nozzles under prolonged high-temperature operation.