GB/T 7476-1987 is a water quality testing standard, and the EDTA Titrimetric method is used to determine the calcium content in water. Calcium content is an important indicator of water quality, which affects water Hardness and various industrial and domestic applications. The standard specifies the operation process of the EDTA Titrimetric method in detail, including reagent preparation, titration steps and result calculation, etc., which can accurately determine the calcium content in water. This method is suitable for all kinds of water bodies, providing a reliable detection method for water quality analysis, water treatment process optimization and related scientific research work, and helping to ensure water mass.