Abstract: Seed oil of Herpetospermum pedunculosum(Ser.) Baill.was obtained by supercritical carbon oxide extraction.The conditions of exeract were,under pressure of 20 MPa,temperature 45℃,the CO₂ flow rate 35~40 kg/h and dynamic extraction time of 120 min,the method was most selective for the extraction the seed oil(yield 33.35%).And the fatty acids in the extracted oil were analysed using GC/MS.The results showed that the oil contained abundant unsaturated fatty acids.The contents of linolenic acid,linoleic acid and oleic acid were 12.271%,20.149% and 52.282% respectively.This result provide the fundamental data for the further development of Herpetospermum pedunculosum(Ser.) Baill.seed.