The standard GB/T 11911-1989 provides for the direct determination of iron and manganese in water and wastewater by flame Atomic absirption spectroscopy-tometry, AAS. The method is simple, fast and accurate, and is suitable for the determination of iron and manganese in surface water, groundwater and industrial wastewater. The detection limit of iron is 0.03 mg/L, and the detection limit of manganese is 0.01 mg/L, and the measurement range is 0.1-5 mg/L and 0.05-3 mg/L. The iron and manganese content in water is quantitatively analyzed by inhaling the sample into the flame and measuring the Absorbance of the iron and manganese ground state atoms at specific wavelengths. The standard specifies the reagents and equipment required for the test in detail.