Gold nanoparticles (GNPs) are a natural starting point for understanding NP-protein interaction because of their promising features for diverse biomidical applications.In this paper,Spherical GNPs of approximately 14nm were synthesized by Frens’ method and putified by optimal centrifugation operation,characterized using UV–Vis absorption spectroscopy and transmission electron microscopy (TEM).They demonstrated that the purification operation didn`t change the diameter of GNPs.Fluorescence quenching measurement were performed to quantify the interaction of the model GNPs with BSA.The binding constants (Ks) was calculated to be 5.33×108 L/mol (static quenching),which is much greater than those of the binding of proteins with small molecules (typical range 103–106).And the number of binding sites calculated was closed to 1.The result of thermodynamic parameters at different temperatures indicated that the electrostatic interactions is major for GNPs-BSA association.