During the industrial-scale smelting process of manganese ore, blast may occur due to the high moisture content of the ore, and drying pretreatment of the manganese ore is needed in the aspects of safety. In the present paper, microwave drying experiments were conducted under different particle size distributions and different microwave power conditions to explore the basic theory of microwave drying characteristics and kinetics of manganese ore, and the experimental data were fitted and analyzed by using thin-layer drying dynamics model. Results indicated that with the increase of the particle size and the microwave power of the manganese ore, the microwave drying rate increased, and accompanied with a promoting on the drying efficiency. For describing the microwave drying process of manganese ore, diffusion approach model was adopted among the commonly used thin-layer drying kinetic models. Based on Fick's second law, it can be seen that the surface diffusion coefficient increased from 4.27 x 10(-13) m(2)/s to 8.24 x 10(-8) m(2)/s with the increase of particle size from a particle size range of 0.012-0.095 mm to a particle size range of 4.2-5.0 mm. Clearly, the particle size has a significant influence on microwave drying efficiency. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.