Bifidobacterium lactis Probio-M8 is a milk-derived probiotic with excellent probiotic properties. Solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS) was used to investigate the effect of the addition of Bifidobacterium lactis Probio-M8 on the volatile flavor substances in fermented milk， and compared with Bifidobacterium lactis BB-12， to evaluate the fermentation， storage and sensory characteristics of fermented milk. The results showed that a total of 66 volatile flavor substances such as ketones， acids， aldehydes and esters were detected in the fermented milk， among which 39， 33 and 31 substances were detected in the fermented milk with the addition of Bifidobacterium lactis BB-12， the fermented milk with the addition of Bifidobacterium lactis Probio-M8 and the ordinary fermented milk， respectively. The relative contents of characteristic flavor substances such as diacetyl， acetoin， decanoic acid， hexanoic acid and 2-pentanone were increased in the fermented milk added with Probio-M8， which contributed significantly to the flavor of the fermented milk. Cluster analysis showed that compared with the control group， the relative content and composition of volatile flavor substances in Probio-M8 and BB-12 fermented milk were similar， while acetaldehyde， heptaldehyde and lauric acid were also different. The sensory scores of the BB-12 fermented milk and the Probio-M8 fermented milk showed no significant difference， both of which were significantly higher than those of the ordinary fermented milk (P<0.05)， suggesting that the fermented milk with the addition of Probio-M8 had good flavor and was recognized. In addition， the addition of Probio-M8 could significantly increase the viscosity of the fermented milk (P<0.05) and shorten the fermentation time of the fermented milk， but had no significant effect on the titratable acidity， pH value and water holding capacity of the fermented milk during storage (P>0.05). The viable count of Probio-M8 in fermented milk was (4.35±0.01) × 107 CFU/mL after 28 days of storage at 4 ℃， indicating that the strain had good survival stability and could effectively ensure the probiotic efficacy of Probio-M8. Conclusion: Bifidobacterium lactis Probio-M8 endowed fermented milk with probiotic characteristics and good characteristic flavor at the same time， which provided reference for its application in practical production.