7-ACA is an important mother nucleus of semi-synthetic cephalosporin antibiotics, the quality of which directly determines the quality of various synthetic cephalosporin products.In order to monitor the quality of products, Coomassie Brillian Blue method was used to determine the concentration of protein in 7-ACA, and  the detection method was verified: when detect wavelength was 595 nm, the linearity range was 0.000～100.000 μg,the correlation was 0.999 3,and the average recovery rate was 99.3%（n=3）.This method had the advantages of high precision and accuracy, and it was suitable for the analysis of the concentration of protein in 7-ACA.As a result, the Coomassie Brillian Blue method  could be the method to control the quality of 7-ACA.