Abstract: The particle size of ultrafine silicon carbide powder was measured by laser grainsize analyzer with the distilled water as the dispersion medium.The effects of ultrasonic dispersing power，ultrasonic dispersing time，types of dispersant，content of dispersant，and ratio of shading on the partice size determination of superfine SiC powder were investigated.The optimum determination conditions were obtained as follows：the ultrasonic dispersing power was 200 W，the ultrasonic dispersing time was 10 min，polyethylene glycol（2000） with mass concentration of 2.0 g/L was used as the dispersant，and the ratio of shading was 10.0%.The repeatability and reliability of the data determined by laser grainsize analyzer were fine under these conditions.

Key words: laser grainsize analyzer, silicon carbide, particle size analysis, dispersant