Two new bicyclic diterpene glycosides, lemnaboursides B and C (1, 2), have been isolated from the Chinese soft coral Lemnalia bournei. They are the monoacetate derivatives of lemnabourside (3) previously obtained from the same species. The structures of compounds 1 and 2, which showed weak cytotoxicity against HepA, S180A and EAC cells, respectively, were established from spectral data and chemical transformations.