A novel meroterpenoid, euphoractone (1), was isolated from the extracts of the roots of Euphorbiafischeriana Steud. Its structure was determined by spectroscopic methods and X-ray crystallography. 1 possesses an unusual ent-abietane-phloroglucinol skeleton. The plausible biosynthetic pathway for 1 was proposed. 1 showed inhibitory activities against human lung cancer H23 and H460 cells with the IC50 values of 21.07±3.54 and 20.91±4.07μmol/L.