The volatile oil from the Allium mongolicum Regel flowers by supercritical-CO₂ fluid extraction(SFE) was optimized using response surface methodology(RSM)，and the volatile oil was identified by GC—MS. The effects of the extraction pressure, extraction temperature, extraction time on the yield of volatile oil were investigated by a three-factor and three-level Box-Behnken central composite design with the extraction rate as the response value. The results showed that the optimum conditions for the extraction of Allium mongolicum Regel flower oil were as follows: extracting temperature 39 ℃, pressure 29 MPa, time 1.2 h, CO₂ flux 20 L/ h. Under such condition, the model-predicted and experimental values of oil yield were 19.36% and 18.90%. The 29 chemical components were separated by GC—MS, which were 96.67% of the total oil, and 27 compounds of them were also identified, including 8 aldehydes(37.63%), aromatic hydrocarbon compounds(30.52%) and Gingerol (12.60%).