The dehydration of tetrahydrate potassium pentaborate was investigated in it fluidized bed reactor. The effect of reaction temperature. flow rate of the fluidization gas and particle amount were studied in detail, The optimum dehydration conditions of the reactor were determined at three temperatures (573 K, 598 K and 623 K). In the process of dehydration, only tetrahydrate potassium pentaborate and KB5O5 were observed. The dehydration kinetics of tetrahydrate potassium pentaborate Were also investigated at the same temperatures, and by applying the experimental data to the Shrinking-Core Model, it was found that the dehydration process is controlled by chemical reaction at the beginning period, and thereafter controlled by the diffusion through product layer. (c) 2005 Elsevier B.V. All rights reserved.