Abstract: Object To investigate the chemical constituents from the whole plant of Lysimachia candida Ldl.. Methods The constituents were isolated and purified on silica gel column chromatography.Their structures were elucidated by chemical and spectroscopic evidence. Results A triterpenoid saponin,named candidoside A ( Ⅰ ), was isolated from the extract of n-BuOH. Its structure was shown to be 3β,16α-dihydroxy-olean-12-en-28-al-3-O-β-D-glucopyranosyl-23-O-α-D-ribofuranoside. Conclusion Candidoside A was a new triterpenoid saponin.