Objective: To study the chemical compositions of the essential oil from the leaves of Thalictrum ichangense. Method: The essential oil was extracted by supercritical carbon dioxide extraction assay

and the constituents were identified by gas chromatography-mass spectrometer (GC-MS). The DPPH·method was used to study its antioxidant activity and MTT assay was used to study its anti-tumor activity. The relative content of each component was calculated by area normalization method. Result: Twenty one compounds were identified

representing 91.86% of the essential oil. The scavenging ratio for the DPPH·radicals reaches (61.2±2.1)% when the concentration was 300 mg·L-1 and the essential oil at 300 mg·L-1 showed anti-tumor activities against MGC-803 in vitro with a inhibition rate of (56.0±6.8)%. Conclusion: The principal chemical constituents of the essential oil were tetratetracontane (25.82%)

stigmastan-3

5-diene (16.39%)

and octacosane (14.96%). The essential oil showed certain antioxidant activity and displayed good inhibition proliferation of MCG-803 in vitro. The analytic results can provide further exploitation and utilization of T. ichangense.