Microwave has attracted much attention with respect to coal drying, especially improving the performance of lignite. In this study, the characteristics of dehydration dynamics and changes in the physical structure of lignite under microwave radiation were investigated. The results show that the change process of temperature and moisture is phased in the microwave dehydration period (0-180 degrees C). Moreover, the change in the moisture content of lignite is actually the coupled migration of liquid water and water vapor, and the pressure gradient and temperature gradient formed by uneven evaporation of water under high-power microwave heating not only promote the formation, development, and connection of pores and fractures but also contribute to the movement of water, especially partially liquid water which can directly migrate to the coal surface. Higher moisture content means more intense water movement under microwave heating as well as more significant lignite drying and structural damage effects. The research discussed the correlation between moisture movement and lignite structure, which can provide constructive insight into the efficient application of microwave drying and heat-driven cracking technology to coal.