Abstract: In order to analyze the relationship between selenium and immune ability in dairy cows,a total of 50 lactating cows with the similar age,parity and body condition were randomly selected and divided into control group and experimental group according to the serum selenium level.The contents of IL-2,IL-6 and TNF-α in the blood samples of dairy cows were determined by double antibody sandwich method.The results showed that while the serum content of IL-2 of experimental group was lower than control group,no significant difference was observed (P>0.05);there was a positive correlation between serum selenium level and serum content of IL-2 (R=+0.133,P=0.356);while the serum content of IL-6 of experimental group wase higher than control group,no significant difference was observed (P>0.05);there was a significantly negative correlation between serum selenium level and serum content of IL-6 (R=-0.28,P=0.049);the serum content of TNF-α of experimental group was significantly lower than control group (P<0.05);there was a significantly positive correlation between serum selenium level and serum content of TNF-α(R=+0.311,P=0.028).The combined data suggest that the selenium supplementation with appropriate level can improve the immune ability of dairy cows.