The precession vortex core weakens the trapping efficiency of cyclone to fine particles. In this paper, numerical simulation method was used to investigate the influence of apex cone placed at the dust outlet on the flow field and performance of cyclone. First, the influence of apex cone on the velocity distribution, shortcircuit flow and vortex cone procession characteristics in cyclone separator was analyzed. On this basis, the trapping efficiency for 1 μm particles and the proportion of particles that escaped with shortcircuit flow and back-mixing due to air entrainment were measured. The results show that the installation of apex cone can reduce the procession frequency and deviation of vortex core, thus weakening the particles escape caused by the end of the vortex core sweeping wall of cyclone. Therefore, the installation of apex cone can effectively improve the separation efficiency of cyclone separator.In addition, the installation of apex cone has little effect on the tangential velocity, axial velocity and shortcircuit flow of the airflow in the main separation space of cyclone, and thus the pressure drop is not significantly increased.