Abstract: The monosaccharide composition and antioxidant activity of Scorias spongiosa polysaccharide(SSP) were analyzed. The aim of this study was to investigate the polysaccharide contents and antioxidant activities of Scorias spongiosa extract. The SSP obtained through ultrasound-assisted extraction was characterized, and its monosaccharide composition was studied by high-performance liquid chromatography. The antioxidant capacity was evaluated by 1, 1-diphenyl-2-picryl-hydrazyl(DPPH), 2, 2'-azino-bis(3-ethyl benzothiazoline-6-sulfonic acid) (ABTS⁺·), and ·OH.The polysaccharide extraction rate of Scorias spongiosa was 9.61%. The total sugar content was 70.92±1.530 g/100 g, which was mainly composed of glucose, mannose, and galactose in the molar ratio of 1.35:212:1. SSP had a relatively high antioxidant activity as revealed by scavenging ability tests on DPPH·, ABTS⁺·, and ·OH.Antioxidant assays showed the enhanced potency of SSP with its half maximal inhibitory concentration values of(0.796±0.002), (0.923±0.012), and(1.993±0.026) mg/mL for DPPH·, ABTS⁺·, and ·OH, respectively. This investigation shows that polysaccharide extracts obtained from Scorias spongiosa might be used as bioactive natural sources in the food, and cosmetic industries. Furthermore, we could further study the other biological activities of the polysaccharides.