Abstract:A gel chromatography （GPC） method was established for the determination of the molecular weights and their distributions in protein hydrolyzed formula foods and hydrolyzed protein powder. The samples were extracted with a solvent composed of acetonitrile/water containing 0.05% trifluoroacetic acid. The separation was then carried out on a TSKgel G2000 SWXL gel filtration column under the following conditions： a mobile phase of acetonitrile∶water∶trifluoroacetic acid = 40∶60∶0.05 and a detection wavelength of 221 nm. The molecular weight and its distribution were determined by establishing a calibration curve using protein standards of different molecular weights. The results showed that the linear relationship was good when the molecular weight of the protein standard sample was between 189 Da and 12 384 Da. The standard curve equation was y=-0.357 2x+7.115 3， and correlation coefficient R2=0.99， with good repeatability. The relative standard deviation of the molecular weight distribution of each peptide was less than 10%. The results indicated that the method is characterized by its fast analysis speed， simplicity and ease of operation， high precision， good repeatability， and the ability to quickly determine the relative molecular weight and distribution of protein hydrolyzed formula foods and hydrolyzed protein powder.