Abstract: The mechanisms of the interaction between xanthotoxol(XAL) and bovine serum albumin(BSA) were investigated by fluorescence and circular dichroism(CD) spectrometry, as well as the effects of common metal ions(Fe3+, Cu2+, Zn2+, Cr3+) on the XAL-BSA binding. The quenching constants (kq) calculated by Stern-Volmer equation under 290,297 and 304 K were 6.316×1013,4.402×1013 and 3.554×1013 L/(mol·s), respectively. The result indicated that XAL could quench the intrinsic fluorescence of BSA strongly, and the quenching mechanism was static quenching process. The binding constant (K) of XAL to BSA at 297 K was 3.47×105 L/mol. The addition of metal ions changed the binding constant. The distance between the tryptophan residues in BSA and XAL was 5.29 nm by using Föster's equation, and it decreased after interaction with metal ions. The CD spectrometry demonstrated that the secondary structure of BSA changed after its interaction with XAL, and α-helix content decreased; the secondary structure of BSA was also changed by addition of metal ions and α-helix content further reduced.