Abstract: 【Objective】 Powder metallurgy porous materials are widely used in aerospace, coal chemical, automotive, and electronic industries due to their unique combination of properties, including excellent mechanical performance, high porosity and specific surface area, low thermal conductivity, and high electrical conductivity. The particle size distribution（PSD） of the raw powders is a fundamental parameter that significantly affects the forming process, sintered structure, and ultimately the performance characteristics of the final porous product, such as its filtration accuracy and permeability. To ensure the consistency and reliability of these materials, precise and repeatable PSD analysis is essential. This necessitates a thorough understanding of the key variables in the measurement process itself. This study focuses on 316L stainless steel metal powder, a common feedstock for such porous materials, and systematically examines the impact of various dispersion conditions on the results obtained from laser diffraction particle size analysis.【Method】 The PSD of a single batch of 316L stainless steel powder was characterized under varying dispersion conditions using the Malvern Mastersizer 3000+Ultra. The investigated dispersion parameters included: the type of dispersant, sample quality, stirring speed, ultrasonic dispersion time, refractive index, absorption rate, and shading. The experimental approach employed a controlled variable method, where one parameter was altered at a time while others were held constant at a baseline. This sequential investigation allowed for isolating the effect of each condition on the measured PSD, including metrics like D₁₀, D₅₀, D₉₀, and overall distribution width. To validate the accuracy and effectiveness of the laser diffraction technique under the optimized conditions, the resulting PSD data was compared with statistical data obtained from direct image analysis of powder samples using scanning electron microscopy（SEM）.【Result】 The experimental results demonstrat that each dispersion parameter significantly influences the measured particle size distribution. Inappropriate settings could lead to aggregation, inadequate dispersion, or sedimentation, causing skewed and non-repeatable results. Through systematic testing, an optimal set of dispersion conditions is identified. The most accurate and repeatable laser diffraction results for this 316L powder are achieved when using pure water as the dispersant, a sample quality of 3.5 g, a high stirring speed of 2 600 r/min, an ultrasonic treatment time of 15 minutes, a refractive index of 2.6, an absorption rate of 0.5, and a shading of 10%. Under these conditions, the PSD results show excellent agreement with the SEM image analysis, confirming the validity of the measurement.【Conclusion】 This study confirms that seven key dispersion conditions—dispersant selection, sample quality, stirring speed, ultrasonic time, refractive index, absorption rate, and shading—collectively have a substantial impact on the particle size distribution results obtained via laser diffraction analysis. The selection and precise control of these parameters are not merely procedural but are critical determinants of the accuracy, reliability, and repeatability of the test data. The findings provide a scientifically grounded, optimized protocol for testing 316L stainless steel powders. This protocol offers reliable data support for quality control and research in the production of powder metallurgy porous materials. Furthermore, the methodological approach and insights gained have broad application prospects and can serve as a valuable reference for establishing robust measurement procedures for other similar metal or ceramic powder systems used in advanced industrial applications.