Abstract: Two Co-rich seamount crust reference materials of MCPt-1 and MCPt-2 for platinum group elements (PGEs) with an ultra-fine particle size have been prepared by a jet mill. The raw samples of the reference materials were ground by a ball mill to 74 μm(-200 mesh) powder and then were further processed by a jet mill to ultra-fine size. After well-mixed, the particle size distribution of the samples were tested by a laser particle analyzer. The results of particle size analysis were expressed by the particle size distribution plot and specific particle size. The average particle size MCPt-1 and MCPt-2 were 1.8 μm and 1.5 μm (about 2000 mesh) respectively. The paper also introduced principle and application development of fluidized bed jet mill used in ultra-fine process in standard reference material preparation worldwide. Finally, the importance and problems in ultra-fine sample processing, the significance of ultra-fine sample analysis in scientific research were discussed.