Objective:To study the technology of volatile oils from Bupleurum chinense. by supercritical CO2 fluid extraction(SFE)and analyze its chemical constituents. Methods:The SFE technology was chosen and optimized by an orthogonal-design method. The extraction were separated and identified by gas chromatography-mass spectrometry(GC-MS),and their relative contents were determined by normalization method of area. The chemical constituents of oil from SFE and those from traditional steam distillation extraction were compared. Results:The optimum technological conditions were that the extracting pressure was 25MPa,extracting temperature was 55℃;separatorⅠpressure was 8MPa,separatorⅠtemperature was 60℃;separatorⅡpressure was 6MPa,separatorⅡtemperature was 40℃;extraction period was 3 h;CO2 flow rate was 30~35 kg/h. Twenty-four constituents including hexanal were identified in volatile oils. Conclusion:The SPE method could extract more chemical constituents of volatile oils.