Abstract: Single-factor experiments and orthogonal experiments were used to optimize the process for extracting astaxanthin from H. pluvialis using switchable hydrophilic solvent DMCHA. Acylated carboxymethyl chitosan self-polymers was used to produce astaxanthin nano-capsules. And the antioxidant properties of astaxanthin nano-capsules were explored. The results showed that at the extraction temperature of 35℃,H. pluvialis/DMCHA ratio 1:20 and extracted for 24 h,the extraction rate of astaxanthin was the highest,reaching 85.48% with the total astaxanthin content extracted by Folch method. The astaxanthin load could reach 392 μg/mL. It has been proved by antioxidant experiments that astaxanthin nano-self-polymer was more stable than astaxanthin solution under different pH changes. In addition,astaxanthin nano-self-polymer hydroxyl radicals were stored at 55℃ for 24 h. The hydroxyl radical scavenging rate could still be maintained at 40%,which proved that astaxanthin nano-self-polymer can effectively maintain the oxidation stability of astaxanthin.