Abstract: A practical catalytic method to oxidize α-ionone with molecular oxygen under normal pressure and temperature in the presence of catalyst N-hydroxyphthalimide(NHPI) combined with Co(acac)₂ was developed,and the probable catalytic mechanism was proposed.Influences of the reaction conditions on the conversion of α-ionone and the selectivity of the major product(5-oxo-α-ionone) were investigated,the optimal technical parameters for 5-oxo-α-ionone were optimized.The results show that the primary products were 5-oxo-α-ionone,epoxy-α-ionone,as well as rearrangement products 4-oxo-β-ionone and epoxy-β-ionone,which were characterized by infrared spectroscopy,¹H nuclear magnetic resonance spectroscopy,mass spectrometry and elemental analysis.The yield of 5-oxo-α-ionone and the conversion of α-ionone were 53.4% and 95.0%,respectively,under the conditions of 25% NHPI,1.0% Co(acac)₂(in molar ratio),O₂ pressure of 1.0 MPa,the reaction temperature at 70 ℃,and reaction time of 10 h,the procedure shows a good reprodu-cibility in the parallel experiments.