The ISO 13165-3 standard specifies a test method for the determination of radium-226 content in water quality, using co-settling and γ Light spectrum methods. The co-settling technology is used to settle radium-226 in water with Miscellaneous substances, and the radioisotope in Sediment is analyzed by γ Light spectrum method. This method has high accuracy and Sensitivity, and is suitable for environment water quality monitoring, especially in the detection of radium-226 in drinking water, rivers, lakes and other water bodies. The standard provides a scientific and reliable detection method for water quality monitoring, which helps to evaluate the radioactive pollution in water sources and ensure water quality safety and public health.