Microwave self–made hot air coupled drying system was used to test the temperature and moisture content of potatoes under microwave powers of 600, 900, 1 200 and 1 500 W. The microwave drying curve, drying rate and optimum microwave power density was obtained. The dynamic modeling of potato microwave drying and the effective water diffusion model have also been built. By substituting the effective moisture diffusivity model of potato dices into the COMSOL multiphysics software, the three field coupling model of electromagnetic field, solid heat transfer and dilute material transfer was established. The result showed that the microwave drying rate of potato was in a long period of decline after a brief 270 s acceleration period. The optimum microwave power density of microwave drying was 6 W/g, whose drying model could be described by Page equation. The effective moisture diffusivity of potato dices microwave drying was between 4.35×10–9 – 9.02×10–9 m2/s. The dependence of moisture and temperature of potato on microwave power and heating time was simulated during the process of microwave heating, which provide theoretical basis and data support for potato microwave drying process.