GB 6851-1986 specifies the general principles for setting the value of pH reference reagents. It clarifies the principle, operation process and quality control points of pH reference reagents, covering all aspects from reagent preparation, purity inspection to fixed value measurement. Through rigorous experimental methods and multiple sets of parallel determination, the accuracy and reliability of the determination are ensured. The standard provides the basis for mass control of pH reference reagents, and guarantees their traceability accuracy in fields such as acidity measurement. It is of great significance to chemical analysis, scientific research, pharmaceuticals and many other industries that rely on accurate pH determination. It lays a solid foundation for related testing work.