This study was aimed at isolate human bifidobacterium and identify and study its characteristics. A suspected bifidobacterium strain was isolated from the feces of healthy infants， and its probiotic characteristics and fermentation characteristics were identified and analyzed. The results showed that a strain isolated from stool samples of infants was identified as Bifidobacterium longum and named Bifidobacterium longum subsp. longum i772. Further studies showed that it was sensitive to 25 antibiotics. The survival rate of artificial simulated digestive juice was 3.22%. In vitro intervention of THP-1 cells， Bifidobacterium longum i772 increased the proinflammatory immune factors IL-8， TNF-α and TLR4 by 12.71， 5.71 and 12.56 times， respectively， compared with the control group. In the fermented milk preparation experiment， the addition of Bifidobacterium longum subsp. longum i772 significantly (P < 0.05) improved the mouth viscosity and cohesion of the fermented milk. The above experiments showed that human Bifidobacterium longum subsp. longum i772 had the characteristics of tolerance to artificial gastric and intestinal fluid， regulation of immunity， and was suitable to be added into fermented milk as probiotics.