This standard specifies a method for the determination of methyl parathion, parathion, malathion, digo, dichlorvos and trichlorfon in surface water, groundwater and industrial wastewater by Gas chromatography, CG. This method extracts pesticides from water by chloroform and uses Gas Chromatograph with Flame photometric detector, FPD for determination. For trichlorfon, due to its extreme nature and strong water solubility, it needs to be converted to dichlorfon before determination. The detection range of this method is 10 to 10 g, which is suitable for pesticide pollution monitoring of various water quality.