Abstract: In order to optimize and upgrade the existing cyclone classification equipment and improve the classification effect of narrow-grained separated difficultly materials，aiming at the problem of low classification efficiency of traditional cyclone classification equipment for narrow-grained materials，the swirler port ratio，cone angle，diameter and cone combination were studied by means of numerical simulation test. It is found that the key to improve the classification accuracy of narrow-grained materials is to reduce the probability of medium and fine-grained particles entering the sand. By reducing the diameter of the sand outlet within a reasonable range，increasing the inner diameter of the cyclone，increasing the angle of the cyclone cone，and adopting the combination of the cone and the flat bottom，the efficiency of the cyclone for narrow-grained classification can be improved.

Key words: hydrocyclone, narrow grading grading, classification efficiency, computational fluid dynamics