The polysaccharide from Artemisia selengensis Turcz leaf (ASLP) were extracted by hot water extraction method.The effects of extraction temperature,extraction time,extraction times and solid-liquid ratio on the yield of crude ASLP were studied by single factor experiment,and the extraction process was optimized by response surface method based on the results of single factor experiment.Meanwhile,the amounts of neutral sugar and uronic acid,molecular weight distribution,monosaccharide composition,α-glucosidase inhibitory activity and antioxidant activity of ASLP were determined.The results showed that the optimum extraction process of crude ASLP was as follows:extraction temperature 95 ℃,extraction time 3 h,extraction times 3,solid-liquid ratio 1∶30 (g/mL).The yield of crude ASLP was 17.23%±0.26% by the optimum extraction process.The results of physical and chemical properties study showed that the content of uronic acid of ASLP was 31.70%±0.73%,which was higher than the content of neutral sugar (26.20%±1.56%).The molecular weight determination indicated that ASLP was a widely distributed heterogeneous polysaccharide.It was found from the monosaccharide composition study that galacturonic acid had the highest proportion (which was 38.76%) in ASLP,followed by galactose (22.88%) and rhamnose (10.92%).Furthermore,IC₅₀ of ASLP on DPPH and ABTS⁺ free radicals and α-glucosidase were 0.120 8,0.016 01 and 1.364 mg/mL,respectively,indicating that ASLP has good hypoglycemic and antioxidant activity in vitro.