The extraction conditions of volatile oil from Chinese elder herb by supercritical CO₂ were optimized by single factor experiment and response surface methodology. Flow rate of CO₂, the pressure, temperature and time of extraction were employed to examine the influences of the yield of volatile oil. The chemical constituents were separated and identified by Gas chromatography-mass spectrometry (GC-MS). The optimal extracting conditions were flow rate of CO₂ 25 L/h, extraction pressure 30.5 MPa, at 45.0 ℃ for 2.8 h. The extraction rate of volatile oil from Chinese elder herb was 0.86%. 16 kinds of volatile compounds were separated from Chinese elder herb and accounted for 93.87% of the total extractions. The contents of the more compounds were 3-methylpentanoic acid (29.37%), 3-methylbutanoic acid (13.83%), 4-hexene-1-ol (8.27%), and 3-(ethylthio) butanoic acid (6.46%), respectively.