A kind of automatic backwash fiber bundle filter which is used for filtering the washing BFS water is designed and its properties have been studied. The high density particles in washing BFS water and suspended slag wool are the key factors for the filtering effect. By optimization design of structure, the filter has properties of big particles precipitation, automatic discharge of floating sludge and fixed pressure backwash. Through experimental tests, the results show that: the high density particles precipitation and filter layer regeneration rate are quicker; the ability of automatic discharge floating sludge is higher. Compared with the traditional fiber filters, this kind filter efficiency of this kind filters increases 15%.