Objective Using the Coomassie briliant blue method to solve the problem of the precipitation when detecting the protein content in chitosan.Methods Improving the Coomassie briliant blue method.Results Use the Coomassie briliant blue solution with hydrochloric acid concentration of 5% as stain, stain 15 min , the maximum absorption wavelength is 598 nm. the standard curve of absorbance-protein concentration isy=0.003x+0.017 9.r2=0.991, the linear correlation is good within the protein concentration scope of 5μg/mL~40μg/mL, the lowest detection limit is 1μg/mL, and its recovery is 97.8%~103.7%.Conclusions In this paper, the method of determining the content of protein in chitosan is high accurate, stable, reliable and reproducible, and can be widely used in product testing.