Abstract: Objective To determine the oxidative stress level in peripheral blood of vanadium-exposed workers, as an indication of population health effect of vanadium on human neurobehavioral system. Methods 86 vanadium-exposed workers and 65 non-exposed workers were recruited by cluster sampling. A questionnaire was administered to collect demographic and occupational exposure information. Serum activity of superoxide dismutase（SOD）, inducible nitric oxide synthase (iNOS ) and malonaldehyde （MDA） contents were detected by kit assay. The differences in oxidative stress level between vanadium-exposed and non-exposed workers were compared. Results Vanadium-exposed workers had higher levels of MDA contents than the controls. The total superoxide dismutase（T-SOD）activity in vanadium-exposed workers was significantly lower than that in the controls, which was associated with lowered levels of manganese superoxide dismutase (Mn-SOD) activity. No changes in serum levels of cupro-zinc superoxide dismutase (CuZn-SOD) was found in vanadium-exposed workers. No difference in iNOS activity was found between vanadium-exposed workers and controls. Conclusion Vanadium exposure increases free radical production in serum and reduces antioxidant capacity. But the relationship between vanadium exposure and iNOS damage remains uncertain.