Abstract: The altitude parameters are introduced according to the air flow characteristics at high altitudes. Considering the effects of air characteristics at different altitudes on the temperature of heat sink, the correlations of the convective heat transfer coefficient of plate-fin heat sink proposed by reference［11］ are corrected. The outlet average temperature and the average pressure drop of heat sink are calculated using the corrected correlations. The relative error between corrected results and simulation results is less than 5%, showing that the correction is reasonable. The results of this paper are expected to provide calculation methods and reference data for the thermal design and reliability assessment of inverters and other electrical products at high altitudes.