Abstract: A method for the determination of 15 organochlorine pesticides in water samples was established based on liquid-liquid extraction with n-hexane and gas chromatography with electron capture detector. The internal standard method was used to reduce the systematic errors and improve the analytical accuracy. The detection limits of the method for the target compounds were in the range of 0.6~1.4 ng/L and the recoveries for 20 ng/L standard addition were 84.8%~101.0% with the precision of 1.9%~5.6% RSD (n= 7). The method is suitable for routine analysis of the organochlorine pesticides in groundwater samples.