Abstract: In this paper,coriander cultivated in Gaochun County of Nanjing was used as experimental material to study the antioxidant activity in vivo of water extracts from seeds and mature stems and leaves. The scavenging effect of extracts on reactive oxygen species was analyzed in Caenorhabditis elegans and its protective mechanism on oxidative stress induced by paraquat. The results showed that two kinds of water extracts could significantly reduce the reactive oxygen species accumulation level in nematodes(P<0.05),which was in a dose-depended manner. What’s more,both water extracts obviously improved the survival rate of C. elegans under oxygen stress induced by paraquat,but the minimum effective concentration of water extract from stems and leaves was 1 mg/mL,and the minimum effective concentration of water extract from seeds was 0.1 mg/mL. The results of real-time fluorescence quantitative PCR indicated that the water extracts could distinctly affect the genes expression of daf-2 and daf-16 on the ⅡS signaling pathway related to oxidative senescence. In summary,the coriander extract has positive antioxidant effect on C. elegans in vivo.