Abstract: [Objective]To detect the serum level of trace element of copper in experimental dairy cows and to characterize the variation rule of related indexes.[Method]The experimental dairy cows used in this study were selected from a dairy farm in Heilongjiang Province,and were reared under free-choice feeding system with TMR diets.According to the DHI data,50 lactating cows with similar body weight,parity (2-3 times),lactation period (0-10 days),body condition and feeding management were randomly selected.[Result]The correlation between serum copper level and IL-2 content in the experimental dairy cows was R=0.355,P=0.011.There was a significantly positive correlation between serum copper level and IL-2 content in the experimental dairy cows.The serum content of IL-2 in the lactating dairy cows was increased with the elevation of serum copper level.The correlation between serum copper level and IL-1 content in the experimental dairy cows was R=0.215,and the significance was P=0.133,P>0.05.There was no correlation between serum copper level and IL-1 content in the experimental dairy cows.The correlation between serum copper level and TNF- alpha content in the experimental dairy cows was R=0.185,with a significant difference of P=0.198,P>0.05.[Conclusion]There was no correlation between serum copper level and TNF-alpha content in experimental dairy cows.