The experiment was conducted to study the effects of nano-zinc oxide on antioxidant function in broilers. One hundred and ninetytwo Arbor Acres (AA) broilers at the age of one day old were randomly divided into 4 groups with 4 replicates in each group and 12 birds in each replicate. The zinc sulfate (zinc level of 80 mg/kg) supplemented in diet was the control group (group A). Zinc supplemental levels of 40, 80, 120 mg/kg were groups B, C and D, which were added as nanozinc oxide. The experiment lasted for 6 weeks. The results were as follows: supplemental Zn level of 40 mg/kg, the activity of GSH-Px in serum (21, 42 d) of broiler were significantly increased (P<0.05, P<0.01), the TAOC in serum (21, 42 d) were significantly increased (P<0.01, P<0.01), the content of MDA in serum (21 d) were reduced (P<0.05); Zn supplemental level of 80 mg/kg, the activity of GSH-Px (42 d) was significantly increased (P<0.01), the CAT and T-AOC in liver (42 d) were significantly increased (P<0.05, P<0.01), the activity of T-AOC in serum (21 d) was significantly increased (P<0.05), the content of NO in serum (21, 42 d) were reduced (P<0.05, P<0.01), and enhanced the ability of inhibiting hydroxyl radical (·OH) in serum (42 d) (P<0.05), also enhanced the activity of resisting superoxide anion free radical (O2-·) in liver (21 d) (P<0.05). The results showed that adding proteinbound zinc and nanozinc oxide to diet could enhance antioxidant function in broilers, strengthen the activities of antioxidases and reduce the levels of free radicals, in which supplemental nano-zinc oxide level of 40, 80 mg/kg were optimal levels.