Abstract: Photochemical reduction of uranyl ion by ethanol is investigated using an argon ion laser at wave-length 4880 A. The effects of concentrations of ethanol, nitric acid, uranyl ion and of the temperature on apparent quantum yield of U (Ⅳ) formed are studied. When the deoxygenated sample-solution 0.01M UO2(NO3)2-1.5M C2H5OH-0.5M HNO3 is irradiated in nitrogen atmosphere, the maximum quantum yield φ reaches nearly .0.8. As HNO3 1.0M,φ decreases with the increase of nitric acid concentration because of the formation of nitrous acid. Experimental results in systems with the presence and absence of sulfamic acid as a suppressor of nitrous acid are obtained. A preliminary discussion is made on the possible mechanism of the photochemical reduction.