This standard specifies a test method for measuring the gelation degree of rigid polyvinyl chloride (PVC-U) products using a torque rheometer. The method is applicable for determining the gelation degree of finished PVC-U products and can also be used to monitor the gelation degree during their processing and molding. The core principle involves mixing the sample in a torque rheometer at specific temperature and rotational speed, characterizing the melting and plasticization process of PVC resin particles through the real-time measured torque change curve, and thereby calculating the gelation degree. This standard provides a unified methodological specification for the application of mainstream torque rheometer brands, such as "HAAKE," in this field.