Copper (Cu) is an important microelement for the maintenance of normal metabolism of dairy cows and a variety of enzymic composition. When Cu deficiency is occurred in dairy cows, it’ll be accompanied by many diseases. The main objective of the present study was to explore the correlation between Cu deficiency and oxidative stress of lactating dairy cows and evaluate early-warning index for Cu deficiency. There were divided into two groups based on serum Cu levels: a Cu deficiency group and a control group. Serum levels of ceruloplasmin (CP), superoxide dismutase (SOD), total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-PX), and Cu were analysed. The results showed that CP levels in the Cu deficiency group were significantly lower than in the control group, while T-AOC levels were significantly higher, but there were no significant differences between SOD and GSH-PX levels. Pearson correlation analysis showed that serum CP levels were very significantly positively correlated with Cu deficiency, while serum T-AOC levels were very significantly negatively correlated and SOD and GSH-PX serum levels showed no correlations. Logistic regression analysis showed that CP was a risk factor for Cu deficiency, ROC analysis showed that CP had diagnostic value for Cu deficiency, with a critical value of 13.7 U/l. Hence, CP and T-AOC levels in lactating cows showed strong correlations to Cu deficiency, indicating that serum CP can be used to predict Cu deficiency.