Abstract: In this study, the gas-liquid volumetric mass transfer coefficient is estimated by using the oxygen dissolution method in a three - phase circulating fluidized bed reactor of 140 mm inner diameter and 3.0m height. The volumetric mass transfer coefficient kLa is obtained from the measured bulk concentration of the liquid phase by fitting to the axial dispersion model. The influences of the main operation conditions, including superficial gas velocity, superficial liquid velocity and solid circulating rate, are studied systematically. The experimental results are compared with previous researches that were conducted in conventional three-phase fluidized beds.