This standard specifies the method for determining the viscosity value (viscosity number) of polyamide for plastics. The viscosity value is an important index for evaluating the molecular weight of polyamide and its processing performance, and is of great significance for material quality control and application design. The standard describes in detail the test equipment, reagent selection, sample preparation, operation steps and the result calculation formula to ensure the accuracy and repeatability of test results. This method is suitable for many types of polyamide materials, including nylon 6 and nylon 66, etc. It provides a unified technical basis for the research and development, production and quality control of polyamide materials, and helps to improve the performance Stability and application Reliability of polyamide products.