This experiment was conducted to study the effects of peroxide value of duck oil on growth and slaughter performance, organ index and plasma antioxidant, immune, antibody index of broilers. A total of 108 healthy one-day-old Arbor Acres (AA) broilers were randomly divided into 6 groups with 3 replicates per group and 6 broilers per replicate. Broilers in the control group were fed a basal diet, and others in duck oil groups were fed basal diets supplemented with 3% duck oil with 3.8, 17.0, 30.0, 43.0 and 56.0 meq/kg peroxide values, respectively. The pre-experimental period lasted for 7 days, and the experimental period lasted for 28 days. The results showed as follows:1) the average daily gain of 30.0, 43.0 and 56.0 meq/kg duck oil groups was significantly lower than that of the control group (P<0.05), the feed to gain ratio of 56.0 meq/kg duck oil groups was significantly higher than that of the control group (P<0.05). 2) The indexes of spleen, thymus of 30.0, 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05), the kidney index and small intestine thickness of 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05), the gizzard index of 56.0 meq/kg duck oil group was significantly lower than that of the control group (P<0.05). 3) On 15 and 35 days of age, the catalase, hydroxyl radicals activities and total antioxidant capacity in plasma of 30.0, 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05), and the plasma malondialdehyde content was significantly higher than that of the control group (P<0.05); the activities of superoxide dismutase and glutathione peroxidase in plasma of 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05). 4) On 15 days of age, the contents of interleukin (IL)-4, IL-6, immunoglobulin (Ig)A and IgG in plasma of 30.0, 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05), and the contents of interferon-γ (IFN-γ), IL-2 and IgM in plasma of 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05). On 35 days of age, the contents of IL-2, IL-4, IL-6, IgA, IgG and IgM in plasma of 30.0, 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05), and the plasma IFN-γ content of 43.0 and 56.0 meq/kg duck oil groups was significantly lower than that of the control group (P<0.05). 5) On 15 days of age, the levels of infectious bursal disease virus antibody (IBDV-Ab) and newcastle disease virus antibody (NDV-Ab) in plasma of 30.0, 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05), and the plasma H₉N₁ avian influenza virus antibody (H₉N₁-Ab) level of 43.0 and 56.0 meq/kg duck oil groups was significantly lower than that of the control group (P<0.05). On 35 days of age, the levels of IBDV-Ab and H₉N₁-Ab in plasma of 43.0 and 56.0 meq/kg duck oil groups were significantly lower than those of the control group (P<0.05), and the plasma NDV-Ab level of 56.0 meq/kg duck oil group was significantly lower than that of the control group (P<0.05). It is concluded that high peroxide value of duck oil can decrease the growth performance, antioxidant function and immune function of broilers. The peroxide value of duck oil in diet should not be higher than 17.0 meq/kg.