Abstract: Photochemical reduction of UO2(NO3)2 and production of HNO2 in 30% TBP-kerosene solution are investigated using an argon ion laser with 488 nm monochromic beam, and the effects of some, factors on quantum yield have also been studied. The main degradation products of TBP in photochemical process are detected as DBP and butyl aldehyde,and nitrous acid is also found in TBP organic solution at higher temperature (greater than 30℃). The quantity of nitrous acid is proportional to the power of light and concentration of uranyl nitrate and decreases with the increase of concentration of nitric acid at higher acidity. Possible mechanisms of the photochemical reaction are proposed.