2-Nitro-4-methylsulfonylbenzoic acid was synthesized by the oxidation of 2-nitro-4-methylsulfonyl toluene with hydrogen peroxide in the presence of CuO/Al2O3, which was first used in strong acid system.Furthermore, the process of the reaction was thoroughly investigated by varying reactant molar ratio, reaction temperature and the amount of catalyst to obtain the optimum process.Meanwhile, unreacted 2-nitro-4-methylsulfonyl toluene can be recycled after simple treatment.The yield can reach 78.3 %.This method demonstrated the following advantages: Firstly, the oxidant dosage of sulfuric acid and hydrogen peroxide will be reduced greatly.Secondly, unreacted 2-nitro-4-methylsulfonyl toluene can be recycled.Thirdly, this process had good performance on safety.It will be a high-efficiency, energy-saving and environmentally-friendly technol. to produce 2-nitro-4-methylsulfonylbenzoic acid.