Abstract: Photosensitized oxidative desulfurization of thiophene in noctane/water extraction system was studied with riboflavin as photosensitizer and O2 in air as oxidant. A 500W high pressure Hg lamp was used as the light source for irradiation and air was introduced by a gas pump for supplying O2. The desulfurization yield of thiophene was 85.4% for a 3h photoirradiation under the conditions with the air flow at 150mL/min, water/oil ratio at 1∶1 and riboflavin concentration at 30μmol/L. The mechanism of photosensitized oxidative of thiophene is 1O2 exited from 3O2 by the addition of riboflavin. Under the above conditions, the photooxidation kinetics of thiophene with O2/ riboflavin is firstorder with a rate constant of 9.10×10-5s-1 and halftime of 2.12h.