The interaction conditions between the water-soluble chitosans(WSC) and bovine serum albumin (BSA) was studied by Ultraviolet-visible absorption and fluorescence spectrometries. It was shown there was a good linear relationship between the absorbency A and the BSA concentration(0~1.5g/L) and WSC concentration (0~1.5 g/L). The fluorescence quenching of WSC to BSA was static quenching. When the temperature is 30°C, its binding constant Ka=5.35×104 L/mol, binding site n=1.05. The influence of WSC on the conformation of BSA was analyzed by sychronous fluorescence spectra and three-dimensional fluorescence spectrum.