Ultrasound assisted water extraction method was used to extract Radix Hedysari polysaccharides from Radix Hedysari. Based on single factor experiments [ultrasound time, ultrasound temperature, solid-liquid ratio (g:mL), extraction frequency, and particle size], the three factors that have the greatest impact on the extraction rate of Radix Hedysari polysaccharides [ultrasound time, ultrasound temperature, solid-liquid ratio (g:mL)] were selected. Response surface methodology was used to optimize the extraction process conditions of Radix Hedysari polysaccharides. The scavenging ability of Radix Hedysari polysaccharides against 2,2"-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS+) radicals, 1,1-diphenyl-2-picrylhydrazyl (DPPH radicals), superoxide anion radicals, and hydroxyl radicals, the inhibitory effect of tyrosinase monophenolases, as well as the moisture-absorbing and moisturizing properties were investigated. The results showed that ultrasound-assisted water extraction of Radix Hedysari polysaccharides from the powder of 45 mesh in particle size was carried out under the following conditions: ultrasonic power of 99 W, ultrasonic time of 43 min, ultrasonic temperature of 70℃, and material-liquid ratio (g:mL) of 1:21, and polysaccharides were extracted for three times, and the polysaccharides extraction rate was 23.90%±0.38%; The clearance rate of ABTS+ free radicals by Radix Hedysari polysaccharides at a mass concentration of 1.00 mg/mL was 89.67%, and the half inhibitory mass concentration (IC50) was 0.40 mg/mL; The inhibitory rate of Radix Hedysari polysaccharides with a mass concentration of 10.00 mg/mL on tyrosinase monophenolase is 54.14%, and the IC50 value is 8.06 mg/mL; Within 12 hours, in an environment with a relative humidity of 43%, the moisture absorption rate of Radix Hedysari polysaccharides (the percentage of the total mass of Radix Hedysari polysaccharides after water absorption to the mass of polysaccharides before water absorption) was 101.01%, and the moisture retention rate of Radix Hedysari polysaccharides reached 99.87% at a mass concentration of 10.00 mg/mL.