This standard specifies the use of dithiohydrazone Spectrophotometric method, spectrophotometry method for the determination of trace zinc in water, suitable for samples with zinc concentration of 5 to 50 μg/L in natural water and some wastewater. The method forms a red chelate between zinc and dithiohydrazone in a specific pH range and is extracted with carbon tetrachloride for spectrophotometric determination. Interfering substances such as lead, copper, mercury, etc. can be eliminated by using masking agents such as sodium sulfate. The detection limit of this method is 5 μg/L, which is suitable for the determination of zinc content in environment monitoring and water quality analysis.