This standard applies to the determination of HCH and DDT in surface water, groundwater and some wastewater, using Gas chromatography, CG. The water sample is purified after petroleum ether extraction and determined by Electron capture detector, CRP. The method has high Sensitivity and is suitable for the detection of low-concentration pollutants, but attention should be paid to the influence of organophosphorus pesticides and other interfering substances in the sample, which can be removed by concentrated sulfuric acid treatment. The standard provides detailed reagent preparation and Chromatography Column prepative method.