Astaxanthin is one of the carotenoid with strong antioxidant. The conditions of extraction of astaxanthin from Portunus trituberculatus were optimized in this work. Six factors of conditions such as, extraction method, extraction solvent, ratio of solvent to raw material, temperature, and time, were investigated. For the increase of the extraction yield, ionic liquids were used as additives in the extraction solvent. The optimum extraction conditions were found: heat reflux extraction, Dichloromethane/methanol (25:75, v/v) as solvent, 1:30 of the ratio of solvent raw material, $80^{circ}C$, 90 min, and ionic liquid as additive. As a result, 45.81 ${mu}g/g$ of astaxanthin was extracted from waste.