The investigation of wet air oxidation of cerium(III) (Ce(III)) of rare earth (RE) hydroxides was carried out in this work. The effects of air flow rate, reaction temperature, reaction time, solution pH, and anions of F and PO43- on the oxidation rate were investigated. Under the conditions of air flow rate of 3 L min(-1), reaction temperature of 80 degrees C, reaction time of 4 h, and pH 13, the oxidation rate of Ce(III) could reach nearly 97%. According to the kinetics study of oxidation, the reaction order for wet air oxidation was found to be 1 with respect to the concentration of Ce(III) in the suspension at a temperature range of 40-80 degrees C, and the apparent activation energy was calculated to be 10.49 kJ mol(-1). The investigation of oxidation processes in practical systems indicated that RE-hydroxides, which contained fluorine and phosphor and were derived from the treatment of Bayan Obo mixed RE concentrate, could be successfully oxidized by air.