Artemisia　selengensis　Turcz　possesses　various　health-promoting　functions.　However,　the　available　information　regarding　the　structure　and　biological　activity　of　polysaccharides　from　A.　selengensis　Turcz　(APS)　is　still　limited.　In　the　present　study,　the　preliminary　structure,　antioxidant　and　immunostimulatory　activities　of　a　polysaccharide　fraction　from　APS　(APS1)　were　investigated.　Results　of　Fourier　transform-infrared　spectroscopy　(FT-IR),　gas　chromatography-mass　spectrometry　(GC-MS)　and　nuclear　magnetic　resonance　(NMR)　analyses　showed　that　the　main　chain　of　APS1　was　made　up　of　T-alpha-D-Glcp-(1　-＞,　-＞　4)-alpha-D-Glcp-(1　-＞　and　-＞　4)-alpha-D-Galp-(1　-＞　residues).　In　addition,　the　moderate　superoxide　and　ABTS　radical　scavenging　activities　and　noticeable　Fe2+　chelating　activity　of　APS1　were　observed.　Furthermore,　the　administration　of　APS1　could　significantly　restore　spleen　and　thymus　indexes,　increase　the　levels　of　serum　hemolysin　and　lysozyme,　and　improve　the　liver　function　by　remarkably　preventing　the　elevation　of　MDA　level　and　increasing　the　levels　of　catalase　(CAT),　total　antioxidant　capacity　(T-AOC),　superoxide　dismutase　(SOD)　and　glutathione　peroxidase　(GSH-Px)　in　cyclophosphamide-treated　mice.　These　results　suggested　that　APS1　exhibits　antioxidant　and　immunostimulatory　activities　with　potential　application　in　functional　foods.　Copyright　(C)　2019　Elsevier　B.V.　All　rights　reserved.