Objective To establish a gas-mass spectrometry method for determination of epichlorohydrin in Metoprolol succinate tablets. Methods The chromatographic column is HP-1MS. Injection temperature is${220}^{\circ }\mathrm{C}$; The injection method is split injection, and the split ratio is${10}: 1$. The heating procedure is to keep the initial temperature at${50}^{\circ }\mathrm{C}$for$3\mathrm{\;{min}}$, then raise the temperature to${80}^{\circ }\mathrm{C}$at a rate of${20}^{\circ }\mathrm{C}/\mathrm{{min}}$for$5\mathrm{\;{min}}$, and to${280}^{\circ }\mathrm{C}$at a rate of${40}^{\circ }\mathrm{C}/\mathrm{{min}}$for$8\mathrm{\;{min}}$. The sample intake capacity is${1\mu }\mathrm{L}$. The ion source is electron bombardment source (EI), ion source temperature is${230}^{\circ }\mathrm{C}$. Mass spectrometry interface temperature is${260}^{\circ }\mathrm{C}$; the monitoring mode of mass spectrometry is SIM. The mass to charge ratios (m/z) are 49, 57 and 62. Results The linear range of epichlorohydrin concentration is${30}\sim {120}\mathrm{{ng}}/\mathrm{{mL}}\left({r >{0.99}}\right)$. The detection limit is${32.37}\mathrm{{ng}}/\mathrm{{mL}}$. The limit of quantitation is${107.89}\mathrm{{ng}}/\mathrm{{mL}}$. RSD of precision is${1.8}\%\left({n = 6}\right)$. The average recovery is${103.8}\%$with RSD of${2.5}\%\left({n = 6}\right)$. Epichlorohydrin was not detected in 3 batches of Metoprolol succinate tablets. Conclusion The established gas-mass coupling method is simple, practical, accurate and reliable, and can be used for the determination of epichlorohydrin in Metoprolol succinate tablets.