This standard specifies the test method for determining the viscosity of plastics using the falling ball viscometer method. The inclined tube method calculates the dynamic viscosity of the sample by measuring the falling time of the sphere in the liquid sample. It is suitable for the viscosity determination of transparent or translucent plastic liquids and melts. This standard describes in detail the requirements of the test equipment, the setting of the test conditions, the operation steps and the calculation formula of the results to ensure the accuracy and repeatability of the data. The method is simple and efficient, especially suitable for studying the rheological characteristics of plastic materials, providing reliable technical support for plastic production, quality control and material performance evaluation.