ASTM D7025-09 standard test method specifies the test procedure for assessing the fineness of clean flax fibers. This method helps to accurately evaluate the mass of flax fibers by measuring their fineness, and provides an important reference for raw material selection and production in the Spinning & weaving industry. Standardized fineness tests can determine the suitability of flax fibers and their performance in the Spinning & weaving process. This method is widely used in the quality control and product optimization of flax fibers to ensure mass stability of the final product and provide a scientific basis for the performance of fiber processing and subsequent products.