This standard specifies a method for determining the transient tensile viscosity of polymer melts. Transient tensile viscosity is used to characterize the rheological properties of polymer melts under instantaneous stretching conditions and is widely used in the processing of polymers, especially in processes such as injection molding, extrusion and film stretching. The standard provides experimental equipment, operation steps and Data analysis methods to ensure the accuracy and repeatability of test results. Through this method, the flow behavior of polymer melts during stretching can be evaluated, providing a scientific basis for optimizing processing processes, improving product mass and developing new polymer materials.