Converting milk into fermented milk is a complex and dynamic process that depends largely on the selected fermenter. In this study, we aimed to investigate the potential role of Clostridium butyricum (CB) co-fermentation with traditional fermenters (Streptococcus thermophilus and Lactobacillus bulgaricus) in the improvement of quality characteristics of fermented milks. The results of the study demonstrated that, in comparison to the traditional fermenter group (Y) alone, the CB-complexed Y (3CB-Y) with an optimal addition amount (3×108 CFU/g) significantly enhanced the acidification capacity and elevated the count of live bacteria in the fermented milks (P<0.05). Furthermore, at the 28th day, the water uptake increased by 15.6%, culminating in a more robust and dense structure of the gel network in the fermented milks. This improvement was accompanied by an increase in viscosity (37.99 N.s), which ultimately led to an enrichment in the volatile flavor substances (86 species) and a notable enhancement in the sensory qualities of the fermented milk. This study demonstrated that the appropriate dose of CB combined with traditional fermenter co-fermentation could significantly improve the quality characteristics of fermented milk.