Objective: To establish the optimal conditions for extracting volatile oil from Atractylodes macrocephala Koidz. by supercritical - CO2 fluid extraction ( SFE - CO2 ) and analyze its chemical constituents. Methods: We used orthogonal design to determine the optimal conditions for extracting volatile oil from Atractylodes macrocephala Koidz. by SFE - CO2 and used GC - MS to analyze its chemical constituents. Results: Take the extraction rates of volatile oil as criterion and combine saving energy and time, determined the optimalextracting c...