Bifidobacteria strains with potential probiotic properties were isolated from faeces of healthy adults in Shanghai area by MRS medium and identified by colony morphol. observation and 16 S r DNA gene sequence homol. anal. The dominate strains were screened by 7 L fermenter fermentation test, and the milk was fermented by the dominant strain and the in vivo characteristic research of the fermented milk was studied. The results showed that 3 strains of Bifidobacterium longum(P-1, P-2, P-3) were isolated and identified. Since the fermented milk fermented by strain P-2 with good genetic stability had the highest viable counts in the stable phase, the strain P-2 was identified as the dominate strain and named DD98. The fermented milk had the function of regulating intestinal bacteria, which could significantly increase the expression of beneficial bacteria and reduce harmful bacteria in the gastrointestinal tract of mice(P<0.05). In addition, the fermented milk could maintain the normal body mass and blood routine index of mice, which was beneficial to the growth of mice organs.