Effects of soy protein hydrolysates treated with Protamex on growth and fermentation characteristics of brewer's yeast were studied.Results showed that soy protein hydrolysates with different degree of hydrolysis and fractions varied significantly in growth-promoting activity for the brewer's yeast strains.SP9 with degree of hydrolysis of 19.98% showed the highest growth-promoting activity,and the molecular weight(Mw) of peptides with activity mainly below 3 ku.Supplement of peptides with Mw < 3 ku during fermentation resulted in the increases of biomass,fermentation degree and ethanol yield by 27.0%,15.3% and 25.8%,respectively,and made yeast activity at the stationary phase reach to 90.3%.