The SX series hydrocyclone produced by Haiwang company has simple configuration, low production cost, high capacity, high separation efficiency, strong adjustability and adaptability etc features. The hydrocyclone takes water as medium, which realizes the separation by the density difference of particles, that is the gravity separation method. The slurry with coarse slime were fed into multi-cone hydrocyclone with pressure and then it rotates along the wall of cyclone barrel. Under the effect of centrifugal force and gravity, the high density materials pass through the air column gradually and then flow to the cyclone external rotation flow but the low density materials gradually enter to the central air column in the cyclone so as to realise the separation of materials by the density.