The fluidized bed furnace was designed and produced to synthesize β-SiAlON by carbothermal reduction. The parameters necessary for the design of furnace were decided by the chemical engineering calculation and the experiment. From the synthesis of β-SiAlON using the furnace, the rate of reaction could be distinguished three stages which included rate determining step by the film coefficient of mass transfer. Moreover, the rate of a synthetic reaction and the phase composition of the product were influenced the granular diameters and the Z value of raw material.