The ASTM D8394-21 standard test method specifies an automated measurement method for cotton fiber maturity, fineness, color ribbon width, and micron number. This method uses automated equipment to make accurate measurements of several important indicators of cotton fibers to help evaluate cotton mass and guide cotton processing. By measuring maturity, fineness, color ribbon width, and micron number, the standard provides a quantitative test basis for cotton production, processing, and quality control. This method is characterized by high efficiency and high-precision, which can greatly improve production efficiency and ensure that the mass of cotton and its products meets relevant requirements.