A simultaneous determination method was developed for the reliable screening,quantification and confirmation of 24 allergens in cosmetics by gas chromatography-mass spectrometry（GC-MS）.The 24 allergens were extracted from cosmetics with methanol,then determined by GC-MS with the external standard method under the selected ion mode（SIM）.The calibration curves showed good linearities in the range of 0.2-100 mg/L with correlative coefficients (r2) larger than 0.995.The detection limits were in the range of 2-10 mg/kg,and the average recoveries were 80%-104% with relative standard deviations of 1.8%-9.3%.The method was rapid,accurate and sensitive.The positive detection rate of 24 allergens in 150 samples of 77 patients using cosmetics was 78%,and there was at least one allergen measured value above 10 mg/kg in 81.2% of the positive samples.24 allergens in the cosmetics used by 71 patients were detected out and the detection rate was 92.2%,which at least one allergen measured value above 10 mg/kg was 90.1%.24 allergens are the major allergens in cosmetic contact dermatitis.