Abstract: The interaction between two monascus metabolites and BSA were investigated using fluorescence and UV spectroscopy.The binding mode and thermodynamic parameters between two monascus metabolites and BSA were studied. The results showed that two monascus metabolites have the ability to quench the intrinsic fluorescence of BSA, and the quenching mechanism dynamic quenching.The binding constants of MFA-BSA and MFB-BSA were 3.47 × 1012 , 6.35 ×1012 , 7.94 ×1012 L·mol-1 and 6.90 × 1012 , 1.19 ×1013 , 1.75 ×1013 L·mol-1 at 298, 308, 318K, respectively.MFA was a lower homologue of MFB, with the less lipophilic hexanoyl instead of octanoyl side chain, and these resulted in a less interaction with BSA.