Three ternary Eu(Ⅲ) complexes with general formula of Eu(DBM)3LN (DBM =dibenzoylmethanate, and LN (N= 1-3 ) stand for three different 1,1 0-phenanthroline derivatives)have been synthesized for vacuum deposition films-based electroluminescent devices. The complex Eu(DBM)3L3 (L3 = 2-phenyl-3-[3-(carbazol-9-yl)propyl]imidazo[4,5-f]1,10-phenanthroline) was designed with an effort to combine the electron-transporting phenanthroline platform and the hole-transporting carbazole group into one molecule expecting to improve both electron and hole transporting properties simultaneously. The results show that the variation of the neutral ligands in Eu(Ⅲ) mixed ligand complexes is a simple and effective approach to the improvement in the thermal stability, PL and EL properties of materials. A double-layer device with the configuration of ITO/TPD (50 nm)/Eu(DBM)3L3 (50 nm)/Mgo.9Ago.1 (200 nm)/Ag (100 nm)exhibited Eu(Ⅲ)-based pure red emission with a maximum brightness of 561 cd/m2 at 16 V, and an onset driving voltage of 8 V. A device with the configuration of ITO/TPD (50 nm)/[Eu(DBM)3L3(5 nm):BCP (5 nm)]4/BCP (20 nm)/AIQ (10 nm) Mgo.gAgo.1 (110 nm)/Ag (100 nm) gave high efficient and pure red light emission with a luminance of 1419 cd/m2.