Objective: To screen Bifidobacterium from breast milk and improve its oxygen tolerance under aerobic conditions. Methods: Dilution and spread plate methods were performed to separate and screen Bifidobacterium from breast milk. Their Bifidobacterium identifications were characterized by 16S rDNA sequencing. The oxygen tolerant domestications were conducted through gradual increase of oxygen pressure and alternation of aerobic and anaerobic cultivations. Results: A novel Bifidobacterium strain was isolated from human milk and was identified as Bifidobacterium longum by 16S rDNA sequencing, which was named as MEFZ-2201. The homology between MEFZ-2201 and model strain (accession number in NCBI: ON631733.1) reached 100%. After oxygen tolerant domestication, the highest viable bacteria number of Bifidobacterium longum MEFZ-2201d in aerobic cultivation reached 8.9×10⁹ CFU/mL, which was ten times higher than that of its wild-type strain MEFZ-2201. Whereas, the morphological property and physio-biochemical characteristics of Bifidobacterium longum MEFZ-2201d did not change after oxygen tolerant domestication. The short-chain fatty acid production of domesticated strain Bifidobacterium longum MEFZ-2201d was also significantly higher than that of its wild-type strain even under anaerobic conditions. Conclusion: A novel Bifidobacterium longum strain MEFZ-2201 was isolated from breast milk. The viable bacterium number of its domesticated strain MEFZ-2201d was significantly increased under aerobic conditions, indicating that it would be a potential probiotic strain for further development and utilization.