Saikosaponin O was isolated from Bupleutum smithii Wolff var. parvifolium Shan et Y. Li. Its structure was determinated by NMR methods. From TOCSY and DQF-COSY spectra, the residues of monosaccharides and all their assignments were acquired. The anomeric configurations were obtained by ^3J~H~1~H~2. The HMQC-COSY spectrum was used successfully for ^1^3C assignment since it was difficult to do it only by CH-COSY spectrum. All the glucosidic linkages were obtained from HMBC spectrum based on the ^1H and ^1^3C assignments, NOESY spectrum also gave the concordant result about the configurations and the linkage positions.

Key words: OLEANANE, NMR, HMQC, HMBC