Combined reagent for monitoring water quality and use method thereof

The invention discloses a combined reagent for monitoring water quality. The combined reagent consists of a COD (Chemical Oxygen Demand) detection component, an ammonia nitrogen detection component, an orthophosphate detection component and a nitrate/nitrite detection component, each group of detection components consists of a reagent cover, a cuvette and/or a reagent bottle; each reagent cover is composed of a container cover and a sealing cover, the container cover can seal a cavity opening of a sample cavity of the cuvette, the container cover is provided with a reagent groove used for containing reagents, and by selecting and treating the reagents, the storage life is prolonged, and the carrying amount of the reagents, the use amount of liquid reagents and the number of instruments are reduced. Except the suction step, the other steps only need to replace the container cover and the oscillation cuvette in sequence and place the container cover and the oscillation cuvette into a detector, non-professionals