A new reactive distillation device, the multistage gas/liquid/solid three-phase fluidized bed, has been developed. The flow regimes of the multistage three-phase fluidized bed have been studied and the regimes can be divided into the liquid leakage regime, the dispersed bubble regime, and the coalesced bubble regime. Liquid velocity has a much smaller effect on phase holdups in this device than in conventional three-phase fluidized beds. The three-phase fluidized bed is used as a reactive distillation device for the hydrolysis of methyl acetate. Much higher reaction conversion than the equilibrium value and high catalyst-contacting efficiency are obtained. Different methods of feeding the water into the reactive distillation section are studied.