The invention discloses a water purifying system. The water purifying system comprises a constructed wetland pond, wherein a grating regulating pond, a primary bio-membrane reactor and a secondary bio-membrane reactor are sequentially arranged in front of the constructed wetland pond; the grating regulating pond is provided with a water inlet, a first delivery channel communicating the grating regulating pond and the primary bio-membrane reactor is arranged between the grating regulating pond and the primary bio-membrane reactor, the tail end of the primary bio-membrane reactor and the head end of the secondary bio-membrane reactor are communicated, and a second delivery channel communicating the tail end of the secondary bio-membrane reactor and the constructed wetland pond is arranged between the secondary bio-membrane reactor and the constructed wetland pond. The two bio-membrane reactors are arranged in front of the constructed wetland pond, so that the quality of water entering the constructed wetland pond is effectively controlled, the bio-membrane processing technique and the technique of the constructed wetland are combined, the black and odorous water body is continuouslyefficiently treated, treatment of the polluted water source reaches the higher water quality standard, and the problem of fluctuation of the water quality caused by the surface pollution is prevented.