The interaction of magnolol with bovine serum albumin(BSA) was studied using fluorescence spectroscopy under physiological conditions. The binding constants, K, and the ratio of quantum yields of protein fluorescence for complex and free protein, f, at 298 K, 304 K, and 310 K were obtained; the values were 6.799x10(5) L mol(-1), 5.541x10(5) L mol(-1), and 4.344x10(5) L mol(-1) and 0.17, 0.30, and 0.34, respectively. The standard enthalpy change (delta H degrees ) and the standard entropy change (delta S degrees ) were calculated to be -28.53 kJ mol(-1) and 15.88 J mol(-1) K(-1), which indicated that hydrophobic forces played major role in the interaction of magnolol and BSA. The binding average distance between magnolol and BSA (4.32 nm) was obtained on the basis of the theory of Förster energy transfer.