Abstract: The fermentation tests of proliferation on lactic acid bacteria (LAB) was carried out in bioreactor, the results showed that growth of Streptococcus thermophilus and Lactobacillus bulgaricus were significantly promoted in 12g/100mL skim milk supplemented with soy protein hydrolysates (SPH) . The acid production of LAB on nonfat milk supplemented with yeast extracts and multiplication complex were 2 and 3.12 times than that of control. Then the cell count of LAB reached to 10lg cycle on skim milk supplemented with multiplication complex, which increased 1.0².0lg cycle than control. The parameter of accumulate additional alkali volume and interval additional alkali volume showed that the growth curve of LAB on skim milk ascend slowly, and three waves trend as supplemented with yeast extract, and went up dramatically with addition of multiplication complex. The addition of yeast extract alone can not support the continual growth of LAB, however, the addition of yeast extract and protein hydrolytes together can accelerate it and made it to keep in a high growth level. Much more biomass of LAB on milk with multiplication complex would be obtained and the protein in milk would be utilized sufficiently.