The SL/T 788.1-2019 standard describes in detail a method for the determination of total nitrogen in water using a continuous flow analyzer. It is suitable for the determination of total nitrogen in surface water, groundwater, drinking water, domestic sewage and industrial wastewater. The detection limit of the method is 0.016 mg/L (in N) at a 50mm optical path, and the measurement range is 0.065~ 5.00 mg/L. The method is based on chemical digestion, cadmium reduction and diazotization reactions. The nitrogen-containing compounds in the sample are converted into measurable azo-based compounds, which are analyzed by photometric measurement at 540/550 nm. Some of the reagents used in the experiment are harmful substances, and appropriate protective measures should be taken during operation, such as ventilating equipment, protective clothing and anti-solvent gloves, to reduce the operator's contact with the compound.