Photooxidation of carbonyl sulfide (COS) under UV irradiation and the role of the oxides such as SiO2, Al2O3 and Fe2O3 were investigated by in situ FTIR in a long optical path cell. The major products were identified as SO2 and CO2 by means of IR spectra and GC-MS. SO2 was partially oxidized into SO4 on the surface of the oxides 2? and interior wall of the reactor, which was determined by XPS. The photooxidation is pseudo first order with respect to COS, and the apparent rate constant is approximately 9.30×10?4·s?1. SiO2 and Al2O3 promote the photooxida- tion of COS significantly, but Fe2O3 has no obvious influence on the reaction. The reaction rates in the presence of the oxides or not, rank as: UV + SiO2> UV + Al2O3> UV, UV + Fe2O3. The potentiality of the oxides for promoting the photooxidation of COS implicates that the aerosol particles may contribute to the photooxidation of COS in the at- mosphere. Photooxidation of carbonyl sulfide (COS) under UV irradiation and the role of the oxides such as SiO2, Al2O3 and Fe2O3 were investigated by in situ FTIR in a long optical path cell. The major products were identified as SO2 and CO2 by means of IR spectra and was GC-MS. SO2 was partially oxidized into SO4 on the surface of the oxides 2? and interior wall of the reactor, which was determined by XPS. The photooxidation is pseudo first order with respect to COS, and the apparent rate constant is approximately 9.30 × 10 -4 · s -1. SiO2 and Al2O3 promote the photooxida tion of COS significantly, but Fe2O3 has no obvious influence on the reaction. The reaction rates in the presence of the oxides or not, rank as: UV + SiO2 > UV + Al2O3> UV, UV + Fe2O3. The potentiality of the oxides for promoting the photooxidation of COS implicates that the aerosol particles may contribute to the photooxidation of CO S in the at- mosphere.