The effects of plant essential oil (PEO) on the production performance and immune function of laying hens were evaluated to provide theoretical basis for promoting the natural plant extracts. Eight thousand 1-day-old healthy laying hens were randomly divided into a control group or PEO group, with four replicates per treatment and 1000 hens per replicate. The PEO diet was supplemented with 3g/kg plant extract. Diets were fed for 56 days. The tibia length and keel length were detected on an

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... stomach at the end of the trial. Blood samples were collected on the 28 th and 56 th days to detect the level of C3, C4, IL-1, IL-2, IL-17 and immunoglobulin in the serum. The results showed that, compared with the control, PEO supplementation significantly increased the weight gain rate (WGR) at the 2 nd , 4 th , 5 th and 7 th week (p<0.05), and decreased the WGR at the 3 rd and 6 th week. The tibial length was significantly increased at the 3 rd , 5 th , 6 th and 7 th week (p<0.01), and also the keel length at the 5 th and 7 th week in PEO group. The concentration of IgG and IgM also significantly influenced with PEO supplementation, but there was no significant difference in the complements, C3 and C4, and the IL levels between days 28 and 56. Moreover, no significant difference was observed in body weight and immune organ on day 56. Therefore, we conclude that the addition of PEO could improve the production performance and immune function in laying hens.