The application provides a black water treating device with a biological membrane. The black water treating device comprises a biological reaction groove, wherein a biological rotating disc is arranged in the reaction groove and comprises a rotating shaft and a plurality of rotating discs arranged on the rotating shaft; a guiding pipe is arranged in the rotating shaft; an aeration piece is also arranged at the end part of the rotating shaft and is internally provided with an aeration pipe; the guiding pipe is communicated with the aeration pipe; a plurality of aeration holes communicated with the aeration pipe are formed in the upper surface of the aeration piece; the guiding pipe is communicated with a jet pipe; and the jet pipe is provided with an air inlet and a water flow inlet. According to the black water treating device provided by the invention, due to the addition of the jet pipe, air and water are fully mixed, the mixture enters the guiding pipe and flows out from the aeration holes.