Abstract: The computational fluid dynamic(CFD) technique was used to describe the flow fluid and the classification efficiency in the 428 mm industrial hydrocyclone. Through the model validation, the feasibility of the model was determined. And on the basis of the simulation method, effects of the vortex finder, including the vortex finder diameter, length and thickness, on the performance of the hydrocyclone were studied, focusing on the effect of air core, pressure drop, split ratio, and the classification efficiency. The results show that the different vortex finders have great effect on the performance of the hydrocyclone, especially the vortex finder diameter. The calculated optimal overflow size is， diameter of 180 mm, length of 168 mm, and thickness of 2 mm.