NOVELTY - Biologically filtering fiber bundle comprises suspending some fiber bundle filter cores made of fiber filaments onto filter plates to form material filtering components, mounting at least one material filtering component in the shell of filter or filtering pond to form a filtering layer, culturing and growing microbial films capable of degrading the substance such as organic matters in water on the surfaces of the fiber filaments of filtering layers, and clarifying the water by flowing through the filtering layers loaded with microbial films.    USE - The method is useful for biologically filtering fiber bundle (claimed).    ADVANTAGE - Since the fiber bundle filtering material specific surface area is vast and the porosity of filtering layer is very high, the method is high in biological carrying capacity, biological degrading efficiency, and excellent in quality of discharging water, energy-saving and floor-saving. The washing water downwards flowing evacuation washing mode, or the washing water downwards flowing charge washing mode, or the washing water downwards flowing and upwards flowing alternative washing mode can be used conveniently when washing, the metabolic dead microbial films and the intercepted feculence on the fiber bundle filtering material can be washed out, the washing effect is good, the filtering material is without harden, the amount and quality of discharging water are stable.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is a device for biologically filtering fiber bundle comprising a pressure-type fiber bundle filter and a gravity-type fiber bundle filter, where the device mainly comprises a shell, a filtering material component, a water distribution device, a water collecting device, a washing gas distribution device, a filtering water inlet pipe or channel, a filtering water outlet pipe or channel, a washing gas inlet pipe, and a downwards flowing washing water discharge pipe or channel; the filtering material component is mounted in the shell, the washing gas distribution device is arranged below the filtering material component, the water distribution device is arranged above or below the filtering material component, the water collecting device is arranged below or above the filtering material component, the filtering water inlet pipe or channel is connected with the upper part or lower part of shell, the filtering water outlet pipe or channel is connected with the upper part or lower part of shell, the washing gas inlet pipe is connected with the washing gas distribution device, the downwards flowing washing water discharge pipe or channel is connected with the lower part of shell.