Classifier mainly has spiral classifier and hydrocyclone which is widely used in concentrating plants and watched with ball mill to form closed circulation procedure for the classification of the ore sand or used for the classification of the ore sand and fine silt in gravity mill, used for conducting size grading for pulp in the process of the metal separation and used for the desliming and dehydration in the mine separation. This kind of classifier owns advantages of simple structure, reliable working state and easy operation.