Abstract: The experiment was designed to study the effect of compound biologic premix on the performance and milk quality of dairy cows. Holstein cows were divided into two groups， each with 10 cows， with the similar age， parity， lactating month， gestation period， milk quality and body weight, and were randomly allocated to one of two treatment diets which included the same basal diet. Common compound premix was added in the control diet， and compound biologic premix was added in the test diet. In 74 d experimental period the results showed: the daily milk yield of treatment group was significantly higher than that of control group （P<0.05）. The milk fat percentage was raised by 125% in treatment group， and which was higher than that of control group （P<0.05）. The milk protein and solids percentage was increasing with the extended lactation time， but no significant difference was found between the two treatments （P >0.05）. We can conclude that 5% compound biologic premix supplied in basal diet was helpful to increase the performance of milk yield and to improve the milk quality of diary cows.

Key words: compound biologic premix, dairy cows, performance, milk quality