A new triterpenoid saponin was isolated by bioactivity-guided isolation from 揋ualou-xiebai-baijiu-tang?consisting of Fructus trichosanthisi and Bulbus allii macrostemi. Its structure was determined as 3-O-b-D-galactopyranosylhederagenin 28-O-b-D-xylopyranosyl (16)- b-D-galactopyranosyl ester by means of chemical evidences and spectral analysis. A new triterpenoid saponin was isolated by bioactivity-guided isolation from 揋 ualou-xiebai-baijiu-tang ™ consisting of Fructus trichosanthisi and Bulbus allii macrostemi. Its structure was determined as 3-ObD-galactopyranosylhederagenin 28-ObD-xylopyranosyl (16) -galactopyranosyl ester by means of chemical evidences and spectral analysis.