In order to investigate the heat transfer mechanism of postharvest fruits and vegetables during heat treatment, a universal heat transfer model suitable for columnar and spherical fruits and vegetables was established. The results showed that the established model could well predict the temperature changes of heat-treated fruits and vegetables, and the relative errors between simulated and measured results were lower than 5%. With the same treatment effect, the heating time of the Elizabeth muskmelon treated by the hot water method was only 35%–50% of the heating time of the Elizabeth muskmelon treated by hot air method. The surface heat transfer coefficients of the muskmelons treated by hot water and hot air were 190–250 and 10–30 W/(m2·℃) respectively. The universal heat transfer model and experimental results can provide guidance for operation and optimization of the heat treatment of postharvest fruits and vegetables.