This study took a 10 mm hydrocyclone as an example. We researched and development a 30 mm hydrocyclone with concentric vortex finder. The purpose was to improve the partial separation efficiency and have the effect of multiple classification. The CaCO3 and PMMA was as our material. A numerical software, Fluent, was used for analyzing the distributions of fluid velocity, static pressure, kinetic or the particle tracks. Then use the Fluent to design a new type of hydrocyclone. There were variety of different combinations of overflow pipe in the simulation. Such as the concentric vortex finder which includes the inside pipe is short when the outside pipe is long. The opposite is also true. On the other hand, we compared the single inlet with the double inlet on the hydrocyclone. The simulation results showed that when the size distribution rage of material is large as CaCO3 can improve the reliability with the experimental. If the outside overflow pipe is longer than the inside overflow pipe, it could make the particle separate again with the secondary vortex. The air core could be replaced when we installed a solid cylinder in the cone of hydrocyclone. The result showed that the length of inside overflow pipe and outside overflow pipe are 17.5 mm and 52.5 mm is the best design.