To make full use of Idesia polycarpa resource, the optimum conditions of extracting oil in I. Polycarpa by supercritical CO₂ were studied by single factor and Box- Behnken designs, and the fatty acid composition of this oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the yield of the oil in I. polycarpa extracted by supercritical CO₂ was (38.25±0.41)%, when extracted at 24 MPa and 53 ℃ for 147 min. Moreover, the regression model between yield and influence factors was very significant (P=0.000 9). In addition, the results of GC-MS showed that the total content of unsaturated fatty acid in the oil was 81.33%, and that of linoleic acid was 71.43%. In conclusion, the oil extracted from I. polycarpa is an edible oil resource with high quality, and could be efficiently extracted by using supercritical CO₂.