The flavonoid compounds of Achillea wilhelmsii obtained by using supercritical carbon dioxide (sc-co2) extraction were investigated and the obtaind crude extract yields were compared in order to select the best operation parameters. It must be noted that CO2 was used as the supercritical fluid because it has a moderate critical temperature and pressure.The studied parameter were pressure (150, 170 and 190 bar), temperature (35, 40 and 450C) and dynamic extraction time (10, 30 and 40 min). the optimum exctraction condition occurredd at 190 bar, 450C and 30 min. Based on the mean value, pressure had dominate effect on the extraction yield. In addition, the components of the flavonoid from Achillea wilhelmsii were identified by chromatography analysis.the main components were 43.10% of comphore and 10.01% of carvacrol.