GB/T 24632.1-2009 lays the foundation for the roundness specification. It sorts out professional vocabulary related to roundness, accurately defines terms such as roundness error and ideal circle, and avoids misunderstandings in industry communication. At the same time, it clarifies the key parameters of roundness, including shape parameters, evaluation parameters, etc., and standardizes its calculation and value method. Provide a unified terminology system and quantitative basis for the subsequent measurement, evaluation and application of roundness in product design and manufacturing, help various industries to accurately understand and control roundness, and ensure the mass of round products.