Abstract: This study was to investigate the effects of papain hydrolysis on antigenicity and molecular subunit composition of soybean proteins from traditional raw soybean milk. The contents of antigenicity proteins were measured by enzyme-linked immuno sorbent assay ( ELISA) , the subunits of soybean proteins were researched by SDS-PAGE, and the optimum hydrolysis conditions were studied by the orthogonal test. The results showed that when the soybean milk were hydrolysized at 53 ℃ for10 min with natural p H ( 6.5 ~ 6.8) , while the enzyme concentration was 3500 U/m L, the α', α subunits of β-conglycinin globulins and the acid subunits of glycinin were hydrolysized completely, the contents of basic subunits were decreased obviously.Under this condition, the residual ratio of β-conglycinin globulins reached to 56.6%, while abundant 14 k Da components were generated.