Abstract: Preparation of benzoic acid by liquid-phase catalytic oxidation of toluene is the pivotal step in the production of caprolactam in SNIA technology of Italy. According to the kinetic model and material balance for 4 key components，a novel method for simulating this reactive system was proposed. The influence of operation conditions on benzoic acid concentration was studied. The kinetic model included the effects of benzaldehyde，benzyl alcohol on the reaction. A new group of kinetic parameters were obtained through multiple nonlinear regressions with industrial data. Hooke-Jeeves algorithm was used to solve the problem. The simulation result showed that the error for benzoic acid mass ratio was within 5%. For the actual industrial process，in a reaction temperature range from 164.8 ℃ to 167.2 ℃ and a toluene feed in mass flux range from 79.7 t/h to 104.1 t/h，benzoic acid concentration would increase if the temperature rose or the toluene feed in mass flux decreased.