Abstract: Photochemical oxidation of thiophene in n-octane/water extraction system by using air as oxidant was studied.Results obtained here can be used as the reference of oxidative desulfurization of gasoline because thiophene is one of the main sulfur-containing components in fluid catalytic cracking gasoline.A 500 W high pressure Hg lamp (wave length 365 nm, 0.19 kW·m^-2) was used as the light source for irradiation and air was introduced by a gas pump for supplying O₂.Thiophene dissolved in n-octane was photodecomposed and removed into the water phase at ambient temperature and atmospheric pressure.Thiophene can be photo-oxidized directly to sulfone,sulfoxide, or ethanedioic acid,SO^2-₄，CO₂.The photo-oxidation kinetics of thiophene with O₂ was first-order with rate constant of 4.42×10^-5 s^-1 and half-time of 4.36 h.The desulfurization yield of thiophene in n-octane was 58.9% for a 5 h photo-irradiation under the conditions with air flow at 150 ml·min^-1 and water/oil ratio at 1∶1.The sulfur content could be reduced from 800 μl·L^-1 to less than 330 μl·L^-1.