Determination of protein content by fluorometry was carried out. In this experiment, CdS quantum dots(QDs)that have special spectral properties were prepared with sodium hexametaphosphate as stabilizer and mercapto acetic acid as modifier by hydrothermal synthesis method. Based on the increase in fluorescence intensity after CdS reacted with bovine serum albumin (BSA), a new method for the determination of protein was established. Results show that the fluorescence intensity of system has a good linear relationship with the concentration of BSA in the range of 0.001 43～0.250 mg·mL-1, and the linear equation was F=5 444.301 03+43.327 39ｃ, relation coefficient (r) was 0.996 6, the limit of detection was 0.001 4 mg·mL-1. The method has been used for the determination of protein in milk and egg, and compared with the standard method (biuret method), and the results were satisfactory.