This paper, the second part of a two-paper series, discusses the computational particle fluid dynamics (CPFD) simulation results to clarify the effects of gas leakage on the separation performance of a cyclone. Compared with the experimental results in Part 1 of this two-paper series, the CPFD simulation results showed good agreements on the pressure drop, the overall separation efficiency, and the grade efficiency. Gas leakage would reduce the swirling intensity in the cyclone, make the downward vortex turn upward in advance, and increase the pressure in the standpipe and the cyclone cone. The particle circulations in the cyclone might be enhanced by gas leakage.