The interaction between rhein and bovine serum albumin(BSA) was studied by UV-Visible， fluorescence spectroscopy and circular dichroism in conjunction with electrochemical method. The results indicated that rhein has a powerful ability to quench the albumin’s fluorescence in a static mode. The binding constants(KA) and binding site numbers (n) obtained at different temperatures were 3.67×105, 0.99 (298 K) and 2.60×104, 0.83 (309 K) respectively. According to the thermodynamic parameters the main sorts of binding force of rhein-BSA was fixed as electrostatic. The distance between donor and acceptor in rhein-BSA was 3.28 nm based on the Frster energy transfer theory. Results of the circular dichroism and synchronous fluorescence show that the binding can cause conformation change of BSA.