In this investigation, the fluorescence and FT-IR spectroscopic studies on synthesized Eu-Tb phthalate complexes and mixed solid complexes of europium and terbium phthalates were perfomed. The experimental results of the emission spectra excited by 365nm UV-light showed that the emission peak positions of Eu ( III ) [or Tb ( III )] wer shifted slightly due to the interaction between Tb ( III )and Eu ( III ) ions. However, the fluorescence intensities of one rare eath ion Eu ( III ) [or Tb (III )] were strongly influenced by the other. FT-IR spectra indicated that the coordination structures of carboxyl groups, both in mechanically mixed and synthesized solid complexes, were also changed. These results suggested that there are interactions between Eu ( III ) and Tb ( III ) ions in their mixed complexes.