Abstract：Ternary complexes of rare earth, with cinnamic acid and 1,10-phenanthroline were synthesized and characterized. The interaction between ternary complexes and bovine serum albumins (BSA) was studied by ultraviolet spectrum and fluorescence spectrum. Results show that the absorption intensity of BSA increased with the increasing of the concentration of ternary complexes. Ternary complexes quenched the fluorescence of BSA and it was static quenching. The binding constant (KA) and binding sites of ternary complexes with BSA at room temperature were 0.91×105 L•mol－1 and 2.1, respectively.