This paper aims to study the chemical constituents of Selaginella prostrata H.S.Kung and their α-glucosidase inhibitory activity. A new sesquiterpene,namely seprostrataoid A (1),together with nine known compounds,namely (3S,5R,8S)-5,8-epoxy-6-megastigmadien-3,9-diol (2),(-)-loliolide (3),(3S,5R,6R,7E)-3,5,6-trihydroxy-7-megastigmen-9-one (4),(7R,8S)-ceplignan (5),(2R,3S)-dihydro-2-(3′,5′-dimethoxy-4′-hydroxyphenyl)-7-methoxy-5-acetyl-benzofuran (6),5,5′-dimethoxylclemaphenol A (7),amentoflavone (8),isocryptomerin (9),hinokiflavone (10),were isolated and purified from the 95% ethanol extract of S. prostrata by comprehensive chromatography methods of silica gel column,Sephadex LH-20 gel column and semi-preparative HPLC. All compounds are obtained from  S. prostrata for the first time.In vitro activity results showed that compounds 7-10 had significant α-glucosidase inhibitory activity with IC₅₀ values of 72.14±2.67,42.68±1.54,61.26±4.32 and 55.43±2.17 μmol/L,respectively.