The invention discloses a rotary filter, which comprises (i) a housing, wherein the housing comprises a first washing area, a final washing area and one or more middle washing areas; the first washing area comprises a first washing fluid input area; the final washing area comprises a final washing fluid input area; and each of the middle washing areas comprises a washing fluid input area respectively; (ii) a control head, wherein the control head comprises a first washing fluid output area, a final washing fluid output area and one or more middle washing fluid output areas; and (iii) a filter drum; wherein the filter drum is set in the housing and can rotate in the housing around a shaft; (iv), an apparatus in the washing input area that transfers the washing fluid from the washing output area to the current washing area in a way of flowing opposite to the rotation direction of the filter drum. The invention is characterized in that the rotary filter is used to help the washing fluid flow from a washing fluid input area (IZn) to the same washing fluid output area (OZn) of the same washing area (n), and to the washing fluid output area of the front washing area.