Abstract: Molecular weight distribution and antioxidant activities of each protein composition in germinal black soybean were studied.Protein components in germinal black soybean were extracted and separated by ammonium sulfate method.Molecular weight distribution of each protein component was measured using SDS- PAGE method,and antioxidant activity were studied by free radicals scavenging test and anti- H2O2- induced damaged skin fibroblast test.Molecular weight of proteins in germinal black soybean was concentrated in 140.0~166.0,45.0~72.0,17.0~23.0ku.Results of antioxidant activity tests showed that the protein component of 17.0~23.0ku molecular weight had the best antioxidant activity indicating that low molecular weight germinal black soybean protein had stronger antioxidant activity.