Due to the lack of various biosynthetic pathways,lactic acid bacteria(LAB) are nutritionally fastidious and unable to synthesize some essential amino acids and vitamins,so that the high-density LAB cultures must depend on exogenous essential amino acids,vitamins and other growth factors.The growth kinetics of LAB were carried on the chemically defined media(CDM) of three kinds of nitrogen sources of minimal amino acids,all amino acids and soy protein hydrolysates(SPH).Results showed that: the growth μmax of Lactobacillus bulgaricus and Streptococcus thermophilus in the molecular weight less than 5ku SPH media were 0.215 h-1 and 0.262 h-1,respectively,were about 2 twice all amino acids.The cell density of two LAB in the SPH media were 4 times of all amino acids media.The media of all amino acids were low efficiency for L.bulgaricus and S.thermophilus,which growth maximum rates were 0.10 h-1 and 0.12 h-1,respectively,and the pH values of two kinds of cultures decreased only 4.5 to 5.0.Essential amino acids minimal medium can just meet basic requirements for growth of LAB,less than 5ku soy protein hydrolyzate played a significant role for promoting the proliferation of LAB than all amino acids.The oligopeptides in the SPH was the best nitrogen resource for LAB growth,rather than amino acids.Thus SPH can be applied as a kind of additional nitrogen resource ingredients to enhance growth rate of LAB.