Abstract: A method for the determination of ethanol in blood by GC-MS with auto-headspace sample introduction was proposed.The blood sample or ethanol standard (together with a definite amount of tert.-butanol as internal standard) was placed in the head-space bottle and equilibrated at 60 ℃ for 20 min with moderate-speed-shaking.Definite amount of sample was quantitatively introduced into the GC-MS instrument through the sample introduction loop.Retention time of ethanol and tert.-butanol was found at 1.47 min and 1.56 min,respectively.Linear relationship between values of peak area and mass concentration of ethanol was obtained in the range of 0.01-10.00 g·L-1 with values of detection limit (3S/N) of 0.6 mg·L-1 and lower limit of determination (10S/N) of 1.0 mg·L-1.The values of recovery of ethanol was found in the range from 92% to 105%,with RSD (n=6) less than 7%.