Abstract: OBJECTIVE To develop the GC-MS quantitative method for genotoxic impurity ethyl chloroformate in desloratadine. METHODS CNW CD-ACIDWAX(30 m×0.25 mm, 0.25 μm) column was used with the helium as the carrier gas, the gas flow rate was set at 1.2 mL·min^-1. Through 20:1 split head space injection, the headspace temperature was set at 70℃. The temperature was programmed by holding it for 5 min in a column temperature chamber at 50℃ and then heat up to 80℃ at a rate of 10℃·min^-1, and kept at 80℃ for 3 min. Determined by SIM mode, the quantitative ion of ethyl chloroformate was m/z 63. RESULTS The calibration curve of ethyl chloroformate showed good linearity within the concentration range of 0.05-4.00 µg·mL^-1. All the validation parameters about the method including repeatability, intermediate precision, accuracy, solution stability and durability met the required acceptance of relevant method validation guidance. CONCLUSION The method is accurate, reliable and reproducible, and it is suitable for the determination of ethyl chloroformate in desloratadine.