The SL/T 788.5-2019 standard specifies a method for the determination of hexavalent chromium in water using a continuous flow analyzer, which is suitable for the detection of hexavalent chromium in surface water, groundwater, drinking water, domestic sewage and industrial wastewater. This method has a detection limit of 0.001 mg/L (in Cr) when the detection optical path is 10mm, and the determination range is 0.004 to 0.100 mg/L. For samples with concentrations exceeding this range, it can be appropriately diluted and then determined. The principle of the method is based on the reaction of hexavalent chromium with diphenylcarbazide in an acidic solution to form a purple compound. The concentration of hexavalent chromium can be quantitatively analyzed by measuring its signal value at a wavelength of 550nm. This standard provides a scientific basis for the accurate determination of hexavalent chromium in water quality, ensuring the accuracy and Reliability of water quality monitoring.