The absorption spectra of U(Ⅴ ) species in N, N-dimethylformamide (DMF) with a mercury lamp irradiation have been examined in the region of 500-800nm. In addition to the absorption of U(Ⅴ ) at 755nm a new absorption band at 635nm has been observed. When the solution was acidified with nitric acid both bands of U(Ⅳ)-DMF at 550 and 657nm appeared. These results indicate that the new band at 635nm as well as the 755nm band also belongs to U(Ⅴ ) species. When the irradiated solution was kept in the darkness both bands vanished and no absorption other that of U(Ⅳ) was observed, witch implies that a reversible process between U(Ⅳ) and U(Ⅴ) occurred. The relative intensities of the two bands depend on the acidity of the solution. While the acidity is lower than 9.0×10-3mol.dm-3, the absorption at 635nm increases with increasing the acidity, while that of the 755nm band decreases. When acidity reaches 9.0×10-3mol.dm-3 the absorption at 755nm band almost disappears, but that of the 635nm band still exists and U(Ⅳ) is formed. These results indicate that the absorption of U(Ⅴ) at 755nm and 635nm belong to two different U(Ⅴ) species, UO2+－DMF and UOOH2＋－DMF, respectively.