Abstract: A novel green synthesis of o-nitrobenzoic acid by aerobic oxidation of o-nitrotoluene with aqueous ethanol instead of pure methanol as the solvent and substituted iron porphyrins as biomimetic catalysts was investigated. The effects of six iron porphyrins with different peripheral substituents on the above reaction were studied. It was found that all iron porphyrins had catalytic activity, and the substituents from strong electron donating group (—OH) to electron withdrawing group (—NO₂) had a remarkable effect on the selectivity of o-nitrobenzoic acid and a insignificant effect on the activity (conversion of o-nitrotoluene). Among the six iron porphyrins T(p-Cl)PPFeCl had the highest catalytic activity and selectivity at the same time. By introducing a stronger electron withdrawing substituent, such as —NO₂ or strong electron donating group, such as —OHaround the porphyrin rings resulted in low catalytic activity and selectivity. Moreover, the effects of different process parameters, such as ethanol concentration, NaOH concentration, dioxygen pressure, temperature, reaction time and initial concentration of o-nitrotoluene on the above reaction were examined, and optimal conditions were obtained. The conversion of o-nitrotoluene, the selectivity and yield of product could reach 79. 7%, 95. 8% and 76. 3% respectively by using aqueous ethanol of 80% instead of pure methanol as solvent and T (p-Cl)PPFeCl as catalyst, and the reaction was carried out under optimal conditions, such as NaOH concentration of 3. 75 mol·L^-1, 2. 0 MPa O₂ at 55℃ for 12 h.