The SL/T 788.3-2019 standard specifies a method for the determination of sulfides in water using a continuous flow analyzer. This method is suitable for the detection of sulfides in surface water, groundwater, drinking water, domestic sewage and industrial wastewater. When the detection optical path is 50mm, the detection limit of the method is 0.016 mg/L, and the measurement range is 0.060~ 0.800 mg/L. For samples beyond this range, it can be determined by diluting. The principle of the method is based on the methylene blue formed by the reaction of sulfide and N, N-dimethyl-p-phenylenediamine muriatic acid salt in ferric chloride solution. Color depth is proportional to sulfur Ion concentration, and the measurement signal value is at 660nm wavelength. This standard provides a scientific basis for the accurate determination of sulfides in water quality, ensuring the effectiveness of water quality monitoring.