This standard specifies a method for the determination of chromium, cadmium, lead and arsenic in water treatment agents by Inductance Coupled Plasma Emission Light Spectrometry (ICP-OES), which is suitable for the determination of water treatment agents with the content of these elements in the range of 0.00025% to 0.01%. The standard introduces the process of sample atomization, element ionization and emission Light spectrum detection, provides the guidance of quantitative analysis by External standard method or Standard addition method, and provides an important technical basis for the quality control of water treatment agent products.