Proteolysis of soybean protein isolated(SPI) by A.elegans and R.oligosporus proteases,which were cultured in their optimal enzyme production conditions,under acidic conditions pH3.0～6.0 was investigated.The results showed that,A.elegans and R.oligosporus proteases were able to quickly catalytic soybean 7s and 11s protein degradation when pH was 3.0～3.5,but at the moment,water - soluble protein yield were not high,all under 35%. At pH5.0,5.5 and 6.0,A.elegans and R.oligosporus protease all had stronger catalytic ability of degradation of SPI,both the hydrolysis degree and water-soluble protein increased,but the water - soluble protein yield from A.elegans had always been about 10%higher.SDS - PAGE showed the catalytic rate of A.elegans protease to soybean protein isolated reduced,and appeared with new bands,especially basic subunits was not able to be degraded in four hours.The speed of R.oligosporus protease catalytic degradation of soybean protein isolated was still stronger at pH5.0 and 5.5,but declined obviously at pH6.0,The acidic subunits and basic subunits were not degraded in four hours.In a word,there had big differences between the two proteases on catalysis characteristics at acidic condition.