A new C21 steroidal glycoside, 5beta,6beta-epoxy-glaucogenin C-3-O-beta-D-glucopyranosyl-(1 --> 4)-beta-d-glucopyranosyl-(1 --> 4)-beta-D-cymaropyranosyl-(1 --> 4)-beta-D-oleandropyranosyl-(1 --> 4)-beta-D-oleandropyranoside, named inamoside D (1), was isolated from the MeOH extract of the roots of Cynanchum inamoenum (Maxim.) Loes (Asclepiadaceae). In addition, five known compounds, including 7-demethoxytylophorine (2), dehydrodiconiferyl alcohol gamma'-O-beta-D-glucopyranoside (3), beta-d-fructofuranosyl-(2 --> 1)-alpha-D-(6-O-sinapoyl)-glucopyranoside (4), neohancoside C (5), and cuchiloside (6), have also been isolated. The structure of 1 was determined by 1D- and 2D-NMR spectroscopies. All the compounds were isolated from this plant for the first time.