Abstract: GC was applied to the determination of residual amounts of 20 organochlorine pesticides (OCP′s) in medicine “Sanjiuweitai”. The sample was extracted with n-hexane, and the extract was sulphonated with H2SO4. DB-1701P (30 m×0.25 mm, 0.5 μm) chromatographic column was used for separation in the temperature range from 100 ℃ to 250 ℃ with programmed temperature elevation, and ECD was adopted in the determination. Values of detection limits (3S/N) for the 20 OCP′s were same to be 10 μg·kg-1. Recovery of the method was tested, giving values of recovery ranged from 70.2%-117% and RSD′s (n=6) ranged from 1.0%-1.8%.