The paper presents the results of experimental research on the chemical structure of individual steroidal glycosides spirostane series extracted from solomon^'s seal Polygonatum glaberrimum and conditionally called glycoside B. On the base of classical chemical methods, also IR spectroscopy and chromatography in a thin layer of sorbent was defined that glycoside B represents pentaozid of pennogenin which the carbohydrate chain is composed of three molecules of D-glucose, one molecule of L-arabinose and one molecule of L-rhamnose. The results of experimental researches, as well as their objective analytic judgments give a base to define fully chemical structure of the glycoside B: pennogenin  3-O-β-D-glucopyranosyl-(1→2)-[O-β-D-glucopyranosyl-(1→4)]-O-α-L-rhamnopyranosyl-(1→4)-[O-α-L-arabinopy­ra­no­syl-(1→2)]-O-β-D-glucopyranoside. Fully open chemical structure of the glycoside B has been presented.