This standard applies to ultra-low temperature environments ranging from -196°C to -269°C. It specifies the test method for the tensile properties of unidirectional fiber-reinforced polymer matrix composite laminates, covering specimen preparation, conditioning, testing procedures, and data processing. It enables the determination of key indicators such as tensile strength, elastic modulus, and Poisson's ratio. By applying a uniform tensile force to the specimen, it captures the mechanical response of materials under ultra-low temperatures, providing a basis for material applications in fields such as aerospace and cryogenic engineering. Relevant testing instruments include high-stiffness ultra-low temperature tensile testing machines, liquid nitrogen or liquid helium refrigeration environmental chambers, paired with 0.5-grade low-temperature extensometers, high-precision load sensors, and high-speed data acquisition systems to ensure precise temperature control and accurate test data.