Abstract: The method was proposed to simultaneously determine residues of 4 volatile chemicals (formaldehyde, ethylene oxide, propylene oxide, and 2-chloroethanol) in medical masks by gas chromatography with headspace after optimizing the chromatographic column, split ratio, extraction volume, equilibrium time, and equilibrium temperature. The medical mask was cut into fragments with the size of 5 mm×5 mm. An aliquot (0.5 g) of the sample was placed into a 20 mL-headspace bottle, and 5 mL of water (extraction solution) was added to completely immerse the sample. After sealing, the mixture was analyzed by gas chromatography with headspace under conditions of equilibrium temperature of 80 ℃, equilibrium time of 30 min, and split ratio of 5∶1. CD-624 capillary chromatographic column was adopted as the stationary phase, and targets was detected by the hydrogen flame ionization detector (FID) under programmed heating conditions. It was shown that linear relationships between values of the mass and the peak area of the 4 volatile chemicals were kept in the range of 0.10-1.0 μg, with detection limits (3S/N) in the range of 0.05-0.1 mg·kg⁻¹. Test for recovery was made according to the standard addition method, giving recoveries in the range of 84.3%-92.5%, with RSDs (n=6) of the determined values below 10%. The proposed method was applied to the analysis of medical masks with different brands on the market, but 4 volatile chemicals were not detected.