Objective: To establish a gas chromatog.-mass spectrometry (GC-MS) method for the determination of epichlorohydrin in atenolol.Method: The samples were separated on an DB-624 UI (30 m×0.32 mm×1.8μm) capillary column.The column temperature was maintained at 60°C, and then gradiently raised to 220°C.The flow rate of carrier gas was 1.5 mL·min-1.Selected ion monitoring (SIM) was adopted for mass spectrometry, and m/z was 49 and 62.Results: The assay linearity of epichlorohydrin was confirmed over the range of 0.0354∼0.7088μg·mL-1 (r=0.9999).The average recovery of epichlorohydrin was 98% and the RSD was 1% (n=9).The limit of determination was 0.0177μg·mL-1.Conclusion: The method is sensitive and specific, which is suitable for the determination of epichlorohydrin in atenolol.