A bisdesmosidic cholestane glycoside was isolated from the rhizomes of Polygonatum sibiricum and the structure was elucidated by spectroscopic methods and acid hydrolysis as (22S)-cholest-5-ene-$1{eta}$,$3{eta}$,$16{eta}$,22-tetrol 1-O-${alpha}$-L-rhamnopyranosyl 16-O-${eta}$-D-glucopyranoside. This compound exhibited weak cytotoxic activity with the $IC_{50}$ value, $63.6;{mu}M$ in human MCF-7 breast cancer line, whereas it failed to show agonistic activity at $100{mu}M$ in TGR5 assay with Chinese hamster ovary (CHO) cells. This is the first report of a bisdesmosidic cholestane glycoside from Polygonatum species and the full assignments of $^1H$, $^{13}C$ NMR by HMBC, TOCSY and NOESY experiments were provided.