2-Nitro-4-methylsulfonylbenzoic acid (NMSBA) is usually manufactured from the partial oxidation of 2-nitro-4-methylsulfonyltoluene (NMST) by nitric acid under the catalysis of vanadium pentoxide. This paper reports a novel method for the production of NMSBA from the oxidation of NMST by oxygen catalyzed with a homogeneous catalyst system consisting of H3PW12O40/Co(II)/Mn(II)/Br. The experiments prove that this catalytic system realizes the oxidation of NMST to NMSBA. The optimal phosphotungstic acid concentration is 2500 ppm. The optimum Co(II) concentration is 148 ppm. The highest NMSBA yield is obtained with a Mn/Co ratio of 2.1. The best Br concentration is 1163 ppm. Temperature has a strong effect on the reaction rates. Oxygen partial pressure influences the NMST conversion and NMSBA yield greatly. The kinetic parameters, such as activation energy and reaction orders, have been estimated. (C) 2015 Elsevier B.V. All rights reserved.