Abstract: The Interaction between picric acid ( PA) and bovine serum albumin ( BSA) was studied at the physiological p H by fluorescence and ( UV- vis) absorption spectroscopy, coupled with molecular modeling approach.The experimental results showed that there was a strong fluorescence quenching of BSA by PA. The probable quenching mechanism of fluorescence of BSA by PA was a static quenching by forming the BSA- PA complex. The binding constant and the number of binding sites of PA with BSA at different temperatures were obtained by fluorescence quenching method. According to the van 't Hoff equation, the thermodynamics parameters were calculated, which suggested that the binding pattern was considered from reflection of hydrogen bond and vander Waals forces to thydrophobic interaction. The binding locality was an area 3.14 nm away from tryptophan residue in BSA based on the Foster theory of non- radiation energy transfer. Three competitive sitemarkers revealed that PA was mainly located in the region of site I, molecular docking studies cinfirmed the binding site.Moreover, the results of synchronous fluorescence spectra demonstrated that the conformation of BSA was changed in the presence of PA.