Abstract: The heat shield with large thrust engines is taken as the research object, and a numerical thermal model is established according to the heat transfer mechanism. The transient heat transfer process of the heat shield is simulated for different marginal temperatures, and the calculation results of the transient temperature of the heat shield are in good agreement with the experimental ones, thus the accuracy and the applicability of the model are verified. The heat shield for a certain detector is designed according to this model and the influence factors on the transient heat transfer performance are analyzed. This study provides a basis for the design and the optimization of the heat shield.