The influences of drying temperature and hot air speed on the moisture ratio MR and the drying velocity U of litchi were studied by self-building heat pump drying device. The results showed that drying process of litchi occurred in the falling rate period, and the moisture transfer was controlled by internal diffusion. Nine different dynamic models were fitted nonlinearly by using the drying test data of litchi in the heat pump device. The results of comparing the values of the correlation coefficient R2, the reduced chi-square χ2and the root mean square error eRMSE and the verification testing showed the Page model was the best suitable to descript the relationship of litchi moisture and drying time by hot air drying. The effective moisture diffusion coefficient Deff and the activation energy Ea were also obtained by experiments under different conditions, the values of Deff would increase with the addition of drying temperature and hot air speed, the average value of Ea was 29.939 kJ/mol.