Abstract: In the present investigation four β-diketone complexes of uranyl ion UO2 (AA)2·HAA, UO2 (BA)2·HBA, UO2 (DBM)2·HDBM and UO2 (TTA)2 ·HTTA are prepared, where HAA, HBA, HDBM, and HTTA are acetylacetone, benzoylacetone, dibenzoylmethane and 2-thenoyltrif luoroacetone, respectively, and AA, BA, DBM and TTA are their anions, correspondingly.The complexes are characterized by chemical analyses and infrared spectra. The measurements of the infrared spectra are carried out in the 4000-150 cm-1 range. An approximate assignment is given for some characteristic bands. The relationships between the characteristic bands and the structures of the complexes are also studied.