The particle’s movement and mechanics in the dense media cyclone were analyzed, a proposal that the single direction movement of the light particles was the main movement of particles in the pressure feed dense media cyclone was put forward, which proved that the substantial separating density of cyclone media was higher than the density of suspension, the substantial separating density would be even more higher when the pressure feed dense cyclone media was used. The effective lower separating limit of cyclone was related to the centrifuge field in it, thus, appropriate increase of dense medium cyclone filling pressure can reduce separation threshold, and increase the sorting accuracy.