This work aimed to investigate the heat transfer characteristics of a product with an inner heat source in a packaging container at different pressures. The experimental system of heat transfer characteristics in a packaging container was set up to test the temperature field of a product with an inner heat source in a packaging container under different pressures. The heat transfer characteristics of different parts of the product were discussed and the empirical heat transfer correlations were proposed based on the experimental results. The temperatures of various measure points reached equilibrium more easily under constant pressure than those under low pressure, and the distribution of the temperature field was consistent with the principles of the distribution of thermal boundary layer thickness of heated objects. The convective heat transfer ability was enhanced with the increase of the pressure, and the effect was more significant in a small pressure range. In the normal range of working temperature, the convective heat transfer affected the heat transfer ability of the packaging container greatly, and the convective heat transfer ability was enhanced with the increase of pressure. The empirical heat transfer correlations were obtained within 5% deviation.