Abstract: In this study, the mechanism of the aging improvement of astaxanthin on Caenorhabditis elegans was studied by lifespan extension analysis, oxidative stress, and heat stress analyses. Astaxanthin-treated groups ( 0.8, 1.2, and 1.6 mmol/L) were compared to the control group to explore the anti-aging effect of different concentrations in wild-type nematode and identify the optimal dose according to mean and maximum lifespan extension.The optimal dose of astaxanthin was 1.2 mmol/L, at which dose astaxanthin prolonged mean lifespan of wild type nematode by 41.79% ( p < 0.01) and increased maximum lifespan by 32.72% ( p < 0.01) .The possible mechanisms of astaxanthin 's aging effects were further studied using the1.2 mmol/L treatment to test its impact on resistance to heat and oxidative stress. The mean survival times of astaxanthin-treated wild type nematode after oxidative and heat stress were increased by 22.54% and 24.23% ( p < 0.01) , respectively. In oxidative stress and heat stress experiments, 1.2 mmol/L astaxanthin could significantly increase the survival time of the sir-2.1 mutant nematodes, but had no significant effect on daf-2, daf-16, or eat-2 mutants. The above results suggested that astaxanthin can prolong the lifespan of nematodes by increasing stress tolerance and its mechanism may be related to the insulin signaling and diet-restriction pathways.