Abstract: The interaction of coumarin-3-carboxylic acid with bovine serum albumin(BSA) was investigated by fluorescence and UV spectroscopy. The results showed that coumarin-3-carboxylic acid could quench the intrinsic fluorescence of BSA, and the quenching mechanism was a static quenching process. The number of binding points demonstrated that coumarin-3-carboxylic acid and BSA formed the complex of mole ratio 1∶1. The binding constants and the number of binding sites were determined to be 3.21×10⁴L·mo L^-1，0.974 6（298 K） and 2.00×10⁴L·mo L^-1，0.949 5（310 K）,respectively. The driving forces were mainly hydrogen bond and Vander Waals. Synchronous spectra showed that coumarin-3-carboxylic acid binded to tryptophan residue and changed the microenvironment of tryptophan residue