Abstract: OBJECTIVE To study the spectrum-effect relationship between fingerprint and antioxidant activity of volatile oil from Atractylodis Macrocephalae Rhizoma, and to screen the main antioxidant active ingredients. METHODS GC-MS was used to determine the fingerprint of volatile oil from 15 batches of Atractylodis Macrocephalae Rhizoma from different producing areas. The antioxidant property of volatile oil was determined by removing 1,1-diphenyl-2-picrylonitrile(DPPH) and Fe³⁺ reduction/anti-resistance method. The data were analyzed by partial least squares regression to study the correlation between the fingerprint and antioxidant activity of volatile oil. The active chromatographic peaks were then screened. RESULTS Among the 28 matching fingerprint peaks, the top 5 chromatographic peaks that significantly positively related to scavenge DPPH free radicals were as follow:peak 11 > peak 25 > peak 2 > peak 4 > peak 24. The top 5 chromatographic peaks that significantly positively related to restore Fe³⁺ activity were as follow:peak 11 > peak 8 > peak 14 > peak 19 > peak 26. Peak area of peak 11 was positively correlated with both scavenge DPPH free radicals and restore Fe³⁺ activity. By comparing with the reference substance, it was confirmed that the peak 11 was atractylon. The results showed that atractyrone had significant antioxidant activity. CONCLUSION Atractylon is not only the main component of Atractylodis Macrocephalae Rhizoma volatile oil, but also the main antioxidant active substance.