The novel β-diketone 1-(4-bromophenyl)-3-phenylpropane-1,3-dione (L) was synthesized at room temperature by classical Claisen condensation reaction. With the β-diketone L as the first ligand and phen as the secondary ligand, and a new rare-earth Eu (Ⅲ) ternary complex was prepared. The ligand L and ternary complex were characterized by elemental analysis, IR spectra, UV spectra and fluorescence spectra. IR spectra indicated that: the novel ligand L contained the structure of β-diketone, where the content of enol was high; the Eu3+ ion in the ternary complex was coordinated with six oxygen atoms of three L ligands and two nitrogen atoms of the second ligand phen. UV spectra showed that the main absorption was from the first ligand L in the Eu (Ⅲ) ternary complex. The excitation and emission spectra of the ternary complex were measured and investigated. Fluorescence spectra demonstrated that the ternary complex could emit characteristic fluorescence of rare earth Eu3+ ion and the strongest emission band was narrow which was attributed to the 5D0 →7F2 transitions of the 4f electrons of the central Eu3+ ions. So, the new Eu(Ⅲ) ternary complex is an excellent red-emitter which would be regarded as a valuable material with bright red fluorescence because it presents good monochromaticity.