New complex ［Tb(2,2′-oba)2(phen)2］-(H+3O) (2,2′-oba=2,2′-oxybis(benzoic acid), phen=1,10-phenanthroline) was synthesized under hydrothermal condition and characterized with X-ray single crystal diffraction. Complex reveals mononuclear structure containing TbO4N4 unit. Complex displays the emission peaks at 489, 546, 584 and 622 nm, corresponding to the 5D4→7FJ(J=6-3) transitions of Tb(Ⅲ) ion. The emission band at 546 nm corresponds to the 5D4→7F5 transition of the Tb(Ⅲ) ion, which gives an intense green luminescence output for the solid sample. The recognition for metal ions was discussed with fluorescent spectroscopy. The results show that it has high selectivity for Fe3+ via a fluorescence quenching mechanism. Luminescent investigations reveal that it can detect Fe3+ with relatively high sensitivity and selectivity, even when pH 4.0～8.0, which leads to its application in biotic and environmental system.