Abstract: The effect of Cu²⁺,Fe³⁺,Zn²⁺on the interaction between bovine serum albumin (BSA) and coumarin-3-carboxylic acid was investigated by fluorescence spectroscopy. The results showed that three metal ions have effect on the quenching and combination of coumarin-3-carboxylic acid on BSA, and both the quenching constants and binding constants increased. The hydrophobic effect played an important role in the binding process of two compounds and the type did not changed in the presence of Zn²⁺. The driving force changed to electrostatic interaction in the presence of Cu²⁺and Fe³⁺. It indicated that Cu²⁺,Fe³⁺and Zn²⁺had important influence on the interaction between coumarin-3-carboxylic acid and BSA.