Abstract: The present study was carried on assess the lifespan extension of Caenorhabditis elegans (C. elegans) by astaxanthin (AST) and its related molecular mechanisms. The effect of AST on the lifespan of wild-type (WT) nematodes was observed, the relative expression of antioxidant (sod-3, ctl-1) and autophagy-related genes (bec-1, lgg-1) in WT nematodes was detected by qRT-PCR, the effect of AST on ROS levels in WT nematodes was detected by DCFH-DA fluorescent probe, the effect of AST on LGG-1::GFP fluorescent protein expression in DA2123 nematodes was detected by Western blot, and after oxidative stress was induced by juglone, the mRNA expression levels of bec-1 and lgg-1 in WT nematodes under oxidative stress were detected by qRT-PCR, and the effect of AST on the lifespan of C. elegans under oxidative stress was further examined. The results showed that AST could prolong the lifespan of WT nematodes, up-regulate the mRNA expression levels of sod-3, ctl-1, bec-1, and lgg-1 genes, scavenge excessive ROS in nematodes, up-regulate autophagy levels and prolong nematode lifespan under oxidative stress. Therefore, AST might prolong nematode lifespan by regulating ROS levels in C. elegans and then regulating autophagy.