Objective To optimize the extraction process of Chlorella vulgaris polysaccharides using response surface methodology and analyze their antioxidant activity.Methods The extraction rate of C. vulgaris polysaccharides is used as an evaluation index, and the single factor method is used to select the three factors with the greatest impact on the polysaccharide extraction rate. Box-Behnken design is used to optimize the extraction process. The antioxidant capacity of C. vulgaris polysaccharides is evaluated by DPPH scavenging rate, hydroxyl radical scavenging rate and total reducing power.Results The optimal extraction conditions are determined as follows: sodium hydroxide mass concentration of 1.70 g/100 mL, extraction temperature of 72 ℃, and extraction time of 3.25 h. Under these conditions, the extraction rate of polysaccharides reaches 4.771%. The polysaccharides exhibited significant scavenging effects on both DPPH radicals and hydroxyl radicals, with their half maximal inhibitory concentrations (IC₅₀) being 470 and 850 μg/mL, respectively. Additionally, the total reducing power gradually increases with rising sample concentration, reaching 0.508 when the mass concentration was 100 μg/mL.Conclusion The optimal conditions for extracting polysaccharides from C. vulgaris, optimized by response surface analysis, have practical operability. C. vulgaris polysaccharides have certain antioxidant capacity and hold potential applications in various fields such as food, medicine, and cosmetics.