Abstract: Mechanism of the interaction between chromotropic acid (CMT) and bovine serum albumin (BSA) was studied by fluorospectrometry and UV-Vis spectrophotometry. It was found that significant quenching of fluorescence of BSA appeared due its reaction with CMT. As judged from the fluorescence quenching constants obtained by Stern-Volmer equation, fluorescence quenching of BSA by CMT was attributed to static quenching. The binding constants and number of binding sites were found by applying the model of Langmuir monolayer adsorption. Values of thermodynamic parameters ΔH and ΔS were calculated and based on these results, the binding force of the reaction was recognized to be hydrogen bond and Vander Waals force.