The oxidation of p-tert-butyltoluene (PTBT) by cobalt (11) acetate in acetic acid has been studied kinetically under mild conditions. Under atmospheric pressure, it was found that the oxidation was a first-order reaction with regard to substrate concentration. A 89% yield to p-tert-butylbenzoic acid (PTBA) was achieved under normal pressure at 90degreesC. The oxidation reaction of PTBT under high pressure (0.6 MPa) was also studied and PTBT was oxidized to PTBA in good yields (95%). The industrial process of oxidizing PTBT to PTBA by molecular oxygen containing cobalt acetate catalyst and sodium bromide without solvent was investigated with a view to developing an industrial process for the production of PTBA. A 71.0% yield of PTBA can be obtained at 130degreesC for 8h with promising commercial prospects. The mechanism of oxidizing PTBT to PTBA was presented to clarify the reaction procession of PTBT.