NOVELTY - Treating algae-rich water comprises: (a) feeding water, lifting the raw water to a water-feeding pool by a submersible sewage pump, adding certain pressure to the water-feeding pool to enable the water to flow into a micro algae collector; (b) filtering, arranging multiple micro porous filter membrane micro algae layers in the micro algae collector to form multiple-layer micro porous filter membrane pool, filtering the water with the micro porous filter membrane, discharging the filtered water out of the micro algae collector by a hollow pipe, adsorbing suspension micro algae.    USE - The method is useful to treat algae-rich water.    ADVANTAGE - The method has integral operation of cleaning and collection, thus prolongs working of the system, increases working efficiency of algae-collecting device, and has higher filtering efficiency and micro algae retention ratio.    DETAILED DESCRIPTION - Treating algae-rich water comprises: (a) feeding water, lifting the raw water to a water-feeding pool by a submersible sewage pump, adding certain pressure to the water-feeding pool to enable the water to flow into a micro algae collector; (b) filtering, arranging multiple micro porous filter membrane micro algae layers in the micro algae collector to form multiple-layer micro porous filter membrane pool, filtering the water with the micro porous filter membrane, discharging the filtered water out of the micro algae collector by a hollow pipe, adsorbing suspension micro algae to the inner side of the micro porous filter membrane during filtering to form a micro algae layer; (c) cleaning automatically, opening a pollutant discharging valve at the lower part of the micro algae collector by an automatic control system when the pressure in the micro algae collector is 0.16-2 MPa along with the resistance rise of the micro porous filter membrane and water level rise of the micro algae collector due to the accumulation of the micro algae layer on the micro porous filter membrane, controlling the micro algae collecting brush to clean the micro algae layer, flushing the cleaned micro algae into a micro algae collecting pool by the flushing water which comes from the water-feeding pool and is not filtered by the micro porous filter membrane. An INDEPENDENT CLAIM is also included for a system for treating algae-rich water, comprising a dye pump, a water-feeding pool, a micro algae collector, a micro algae collecting pool, where the water outlet of the dye pump is interconnected with the water inlet of the water-feeding pool. The water outlet of the water-feeding pool is interconnected with the water inlet located at the lower part of the micro algae collector by a water outlet valve. The upper part of the micro algae collector is mounted with a re-flowing hole and purified water outlet. The re-flowing hole is interconnected with the water-feeding pool by a pipeline. The lower part of the micro algae collector is opened with a sewage outlet interconnected with the micro algae collecting pool by a pollutant discharging valve. Multiple micro porous filter membrane micro algae layers are arranged in an inner cavity of the micro algae collector. A micro algae collecting brush capable of cleaning the micro porous filter membrane micro algae layers is equipped at the top part of the inner cavity.