This study was conducted to evaluate the influence of adding eucommin on production performance and immunity function of dairy cows. A total of 40 Chinese Holstein cows were selected based on the same parity, duration of lactation and milk yield, and assigned into two groups randomly. The experimental group was fed with 20g/d eucommin for 75 days, and the control group without eucommin. In addition, another 8 Chinese Holstein with mastitis were fed with 50g/d eucommin for 30 days. The results showed that: 1) There was no influence on milk yield, the fat content had the tendency of increasing in the experimental group, but the lactoprotein reduced significantly (P〈0.05). 2) There was significant influence on somatic count (SCC), and SCC was lower in experimental group than control group. 3) Eucommin had the tendency of increasing the content of |gG, and decreased the MDA content in serum significantly(P〈0.05). There was no influence on the level of SOD, CAT, IgM and IgA. It was concluded that adding eucommin had influence on production performance of dairy cows and had a significant role in the prevention of mastitis, it can improve body immunity and antioxidant capacity to some extent.