The chromatographic separation of the MeOH extract from the aerial parts of Syneilesis palmata led to the isolation of a new sesquiterpene glycoside 4, together with four known compounds. Their structures were characterized to be 4beta,5beta-epoxy-caryophill-8,(15)-ene (1), 3beta-hydroxy-gultin-5-ene (2), 4alpha,5beta-dihydroxy-caryophill-8,(15)-ene (3), (-)-oplopan-4-one-10-alpha-O-beta-D-glucose (4) and 3-hexenyl-1-O-beta-D-glucopyranose (5), based on spectroscopic and chemical methods. Compound 2 showed moderate cytotoxicity against five human tumor cell lines in vitro with its ED50 values ranging from 5.90 to approximately 10.83 microg/mL.