Abstract: The hydrodynamics of a gas -liquid -solid circulating fluidized bed was investigated. A new regime, the three phase circulating fluidization regime, was discovered first time. The characteristics of this regime were compared with that of conventional three phase fluidized regime and transport regime. The particle circulation flowrate, gas and solids holdups in the circulating fluidization regime were studied. In the circulating fluidization regime, the gas and solids holdups can be kept at a relatively high level. Therefore, the three phase circulating fluidized bed provides a new mode of operation for the gas - liquid - solid reactor.