A new derivative of saikosaponin was isolated from the roots of Bupleurum longicaule and identified as 2"-O-beta"-D-glucopyranosylsaikosaponin b2. Its H-1 and C-13 NMR data and the connectivities of the sugar moiety were assigned by use of a combination of two-dimensional NMR techniques (DQF-COSY, HOHAHA, ROESY, HETCOR and HMBC).