Objective: Combined with the determination of macromolecular protein, amino acid and total protein, a quantitative analysis method for the content of small molecular peptides in infant formula milk powder was established. Methods: The contents of total protein, polymer protein and free amino acid in infant formula milk powder were determined by Kjeldahl nitrogen determination method, gravimetric method and ion exchange chromatography, and then the contents of small molecular protein peptide were calculated. Results: The precision RSD of the macromolecular protein detection (n=6) was 0.74%; The recovery rates of the 17 kinds of amino acids were 91.0%~103.2%, and the relative deviations of the detection results were 0.6%~ 2.5%. The recovery rates of small molecular weight peptides were 95.2%~98.2%. Conclusion: The established method has been validated by methodology, with good precision and recovery rate, and can be used for the determination of small molecular peptides in infant formula milk powder.