Electrical conductivity probes were used to measure the radial distributions of solids holdup and liquid velocity in a liquid-solid circulating fluidized bed. These distributions are found to be non-uniform, unlike those in a non-circulating bed. The effects of superficial liquid velocity and particle circulation rate on the radial distributions of bed voidage and liquid velocity are studied. Based on the experimental results, a qualitative explanation is given for the difference between the dispersed fluidization and the circulating fluidization. The effect of the radial nonuniformity of the flow structure on the reactions in the liquid-solid circulating fluidized bed reactor is also discussed.