Water testing agent, preparation process and application method thereof

The invention relates to the technical field of wastewater detection, and particularly discloses a water test reagent, a preparation process and an application method thereof. The water test reagent comprises a component A, a component B and a component C, the component A is prepared from the following components in parts by weight: 10 to 15 parts of potassium dichromate, 16 to 22 parts of mercury sulfate and 160 to 200 parts of mixed acid; the component B is prepared from the following components in parts by weight: 30 to 40 parts of silver sulfate and 4000 to 5000 parts of concentrated sulfuric acid; the component C comprises ferric chloride and aluminum ferric chloride. Silver sulfate in the application has a certain catalytic action, and under an acidic condition, potassium dichromate oxidizes organic matters in wastewater, and the COD content is detected; mercury sulfate masks chloride ions, interference of the chloride ions on COD detection is avoided, mercury ions left in the wastewater are removed thr