Abstract:The hydrolysis of soybean protein isolated（SPI）at neutral protease，for forming soybean protein isolation at different hydrolysis degree（DH）.The surface hydrophobicity，secondary structure and microstructure of SPI have been investigated by using a combination of determination of fluorescence probe，SGS-PAGE and transmission electron microscopy（TEM）methods.The result showed that：with the increase of DH，The surfacehydrophobicity was on the rise.SPI was hydrolyzed to form gradually more low molecular weight peptides，the peptides and base were similar.With the increase of DH，the content of low molecular weight peptides was first increased and then decreased，and the content of the new accumulation peptide was increased.Distribution of SPI at different DH was single globular protein，and relatively loose，the base was distributed on each of the globular protein，sphere surface of most of the globular protein was on subsidence.With the increase of DH，the subsidence of sphere surface of globular protein was obvious，and the base was not dissociation.