A phytochemical investigation on the aerial parts of a Tibetan medicine Meconopsis horridula, by solvent extraction, repeated chromatographies on silica gel, Sephadex LH-20, and preparative TLC techniques, led to the isolation of 9 compounds. By spectroscopic analysis and comparison of its 1H and 13C-NMR data with those in literatures, their structures were identified as oleracein E(1), N-( trans-p-coumaroyl) tyramine (2), chrysoeriol (3), apigenin (4), hydnocarpin (5), p-coumaric acid glucosyl ester (6), stigmast-5-ene-3beta-ylformate (7), 3beta-hydroxy-7alpha-ethoxy-24beta-ethylcholest-5-ene (8), and beta-sitosterol (9), respectively, among which compounds 6-8 were isolated from the genus for the first time,and 1,3 were isolated from the species for the first time. A MTT method was applied to evaluate the cytotoxic activity of compounds 14 against the human hepatocellular liver carcinoma cell line (HepG2), and compound 1 showed significant cytotoxicity against HepG2,with its inhibitory rate of 52.2% at 10 micromol x L(-1).