Abstract: [Objective] This study investigated the effects of a compound probiotic preparation on milk production performance, rumen fermentation status, and serum metabolic parameters in dairy cows, aiming to provide a theoretical basis for improving production efficiency and health management. [Method] Sixty dairy cows with similar parity, milk yield, and body condition were randomly divided into four groups: a control group （Group A）,a low-dose group（Group B）,a medium-dose group（Group C）,and a high-dose group（Group D）.Group A received the basal diet, while Groups B,C,and D received the basal diet supplemented with 4 g/d, 8 g/d, and 16 g/d of the compound probiotic preparation, respectively.The trial lasted 42 days, during which milk yield, milk quality, rumen fermentation status, and serum parameters were monitored and analyzed. [Results] Cows in the medium-dose（C）and high-dose （D）groups showed significantly increased milk yield and improved milk quality. Rumen fermentation health was effectively improved. Serum glucose levels were regulated, and both Total Antioxidant Capacity （T-AOC） and Superoxide Dismutase （SOD） activity increased significantly. [Conclusion] The compound probiotic preparation significantly enhanced milk production performance, improved rumen fermentation status, and regulated metabolic health in dairy cows, demonstrating promising application potential.

Key words: probiotic, milk yield, rumen, fermentation