GB/T 12998-1991 is the technical guidance standard for water quality sampling. Water quality sampling is related to the accuracy of test results. The standard elaborates the purpose of sampling and planning the sampling scheme, covering the selection of sampling points and the determination of sampling Frequency. Explain the collection methods of different types of water samples, such as surface water and deep water, and explain the selection and maintenance of sampling equipment. Emphasize the quality control of the sampling process, including the requirements of sample storage and transportation. Provide comprehensive and standardized operation guidelines for water quality monitors to ensure that the collected water samples can truly reflect the water condition, and lay a reliable foundation for subsequent water quality analysis.