Abstract: p-Xylene oxidation is a complicated gas-liquid-solid three phases process, involving such physical and chemical phenomena as reaction,absorption, distillation and crystallization,etc.A complete reactor model was built to take into account reaction/distillation/crystallization coupling effects.The related basic model parameters were computed based on reaction kinetics,phase equilibria, transport model and crystallization dynamics. The proposed model was solved by the Newton-Raphson method.The model was verified by comparison with commercial unit data and was proved to be enough to simulate the existing commercial units.On the basis of the model, the effects of temperature,residence time and feed mixture ratio and distillation plate number for the oxidation process was further investigated.The simulation results provided directions and means to improve existing units.