Abstract:Three saponins (Ad-Ⅰ, Ad-Ⅱ, Ad-Ⅲ) were isolated from root bark of Aralia decaisneana Hance, and a prosapogenin Ad-Ⅳ was obtained from hydrolysis of Ad-Ⅲ. Their structures were elucidated by spectra (IR, FAB-MS, 1H-NMR, 13C- NMR) and chemical analyses (acid and base hydrolysis), they were araloside A(Ad-Ⅰ), 3-0- [α-L-arabinofuranosyl-(1→4)-β-D-glucuronopyranosyl-]-oleanolic acid (Ad-Ⅱ), 3-O-[β-D-galactopyranosyl-(1→4)-β-D-galactopyranosyl-(1→3)-β- D-glucuronopyranosyl-]-oleanolic acid-28-O-β-D-glucopyranoside (Ad-Ⅲ), 3-0- [ -β-D-galact opyranosyl- ( 1 →4)-β-D-galactopyranosyl-( 1→3 )-β-D-glucuronopyrano- syl-]-oleanlic acid (Ad-Ⅳ). Ad-Ⅰ and Ⅱ are for the first time found in this Plant, Ad-Ⅲ and Ⅳ are new compounds.