The GB/T 17669.5-1999 standard is for the determination of physical performance of building plaster powder. It specifies in detail the specific methods for measuring a number of physical performance indicators of building plaster powder, such as fineness, accumulation density, etc. In the determination of fineness, the screening tools and operation procedures are clarified; in the determination of accumulation density, the instruments and filling methods are standardized. Through this standard, the physical characteristic data of building plaster powder can be accurately obtained, which provides a scientific basis for evaluating its mass, guiding production and construction, and is widely used in building plaster production, testing and related construction fields.