The luminescent enhancement effect of Y(TTA)(3)Phen (TTA = thenoyltrifluoroacetene; Phen = 1,10-phenanthroline) on Eu(III) in Langmuir-Blodgett (LB) films of rare earth complexes mixing with arachidic acid (AA) in a molar ratio of 1:1 and the intermolecular energy transfer from Y(TTA)(3)Phen to Eu(TTA)(3)Phen in the films were investigated in this paper. The compositions of studied films follow the formula of [x% Eu(TTA)(3)Phen + (100 - x)% Y(TTA)(3)Phen]:AA = 1:1 (x = 0, 0.05, 0.1, 0.2, 0.3, 0.5, 30, 50, 80, and 100; in molar percentage). Luminescence intensities of Eu(III) in the films, compared with those that are regulated to no Y(TTA)(3)Phen, were enhanced in varying degrees. They also reveal that the lower the molar percentage of Eu(TTA)(3)Phen that exists in the films, the higher the efficiency of luminescent enhancement that is observed. Meanwhile, the monolayer and multilayer films were characterized by Brewster angle microscopy (BAM), electron diffraction (ED), and UV-vis spectra. The experimental results of BAM and ED show that a crystallization, which corresponds to the plateau in the pi-A isotherm, occurs along with compressing the monolayers. UV-vis spectra indicate that the complexes are transferred onto the substrate successfully. The research on the intermolecular energy transfer proves that the transfer occurs between molecules of Y(TTA)(3)Phen and Eu(TTA)(3)Phen within the distance of 30 Angstrom and belongs to a short-range exchange energy transfer involving the triplet of the ligand.