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Proper design and operating optimization of a multilayer belt dryer are involved in a comprehensive understanding of its drying kinetics in the drying course. To investigate the distributions of material moisture content and temperature in granular bed and the profiles of air humidity and temperature in air channel above granular bed, which are decisive to decisions of dryer structure and operating condition, a mathematical model for simultaneous heat and mass transfer process in a multilayer belt dryer, was established. The numerical simulation based on the model was conducted for a practical drying process of garlic slices in an industrial scale dryer and the calculated results were verified by the collected data from the drying process. Based on the drying kinetic data obtained from the further simulations, the proper parameters of dryer structure, namely, length of belt for each layer, height of air channel between layers and number of belt layers, and operating conditions, namely, height of material bed, belt velocity and air velocity, were discussed.