Abstract: A gas chromatography-negative ion chemical ionization mass spectrometry (GC/MS-NCI) was developed for the rapid determination of endosulfans and its metabolite in soil samples. The soil sample was pretreated with n-hexane and then analyzed by (GC/MS-NCI). External standard calibration was used; the selective ions of endosulfan and endosulfan sulfate were m/z 406, 408，404, 372 and m/z 386, 384, 352 respectively. The detection limit was 0.02-0.03 μg/Kg. The recoveries were in the range of 83.6%～86.4% with the relative standard deviations less than 5%. The method proposed is efficient, accurate and sensitive, which could meet the requirements for determining endosulfans in soil.