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 4$eta$,5$eta$-epoxy-caryophill-8,(15)-ene (1), 3$eta$­hydroxy-gultin-5-ene (2), 4$alpha$,5$eta$-dihydroxy-caryophill-8,(15)-ene (3), (-)-oplopan-4-one-10-$alpha$-O­$eta$-D-glucose (4) and 3-hexenyl-1-O-$eta$-D-glucopyranose (5), based on spectroscopic and chemical methods. Compound 2 showed moderate cytotoxicity against five human tumor cell lines in vitro with its EDso values ranging from 5.90-1 0.83 $mu$g/mL.