In order to optimize the extraction process of polysaccharides from Rehmanniae Radix Praeparata(RRP) and evaluate its antioxidant and anti-aging activities, this study used the analytic hierarchy process-criteria importance through intercriteria correlation(AHP-CRITIC) combined with single factor test and Box-Behnken response surface method to optimize the extraction process of polysaccharides from RRP by ultrasound-assisted deep eutectic solvents (DES). The antioxidant and anti-aging activities were evaluated by DPPH free radical, ABTS cation free radical and hydroxyl radical scavenging experiments and wild-type Caenorhabditis elegans as models. The results showed that the optimum process of ultrasonic-assisted DES extraction of RRP polysaccharide was as follows : choline chloride and urea were combined at a molar ratio of 1∶3, the water content was controlled at 48 %, and the ratio of solid to liquid was 1∶42 (g/mL), the extraction temperature was 73 ℃, the ultrasonic power was 500 W, and the extraction time was 46 min. The polysaccharide yield was 15.07 %. The scavenging rate of the polysaccharide on free radicals in the three modes reached 75.53%, 73.86% and 65.95%, respectively. At the same time, compared with the blank group, the average life expectancy of the nematodes treated with the polysaccharide increased by 9.09%, and the survival time under oxidative stress and heat stress increased by 17.68% and 33.33%.A green and efficient extraction process of polysaccharides from RRP was established, which could provide theoretical reference for the development and application of RRP resources.