Abstract: To discussion the extraction technology of garlic essential oil by supercritical fluid and to analysis the compositions of garlic essential oil ,the effect of extraction pressure, temperature, flow rate and time on essential oil yield were studied. Moreover , the components of essential oil were also analysised by GC-MS. The results were as follows: the optimum extraction pressure, temperature ,CO2 flow rate, extraction time for the extraction were 30Mpa, 45℃,10kg/h and 80min, respectively.24 components which most of them were surfur-containing compounds were found in garlic by GC-MS method .