Abstract: In this paper, a novel experimental technique for gas-liquid-solid reaction was developed to study kinetics of p-xylene oxidation under the condition of high temperature and pressure. Methyl and aldehyed oxidation during the p-xylene oxidation process was studied according to radical reaction mechanism and recycling of the cobalt-manganese-bromide catalyst. The coupling effect between catalysts and radical reactions was analyzed in detail, and a kinetic model was developed based on the proposed mechanism.Model parameters were determined by data fitting.The model agreed well with the experiments.