NOVELTY - An underwater sludge lifting device comprises two parallel boat floaters on water surface and crossing bridge type support which are integrally connected to form I-shape, 7-shaped drainage cylinder fixed below central section of bridge type support, propeller provided on central line of vertical section of drainage cylinder, driving shaft of propeller which is driven by motor on bridge type support, straight suction cylinder arranged at lower side of drainage cylinder, shaft arranged into through hole, and port which is in contact with surface of underwater sludge.    USE - Underwater sludge lifting device used as aerator and fast switch for water treatment field e.g. water sediment processing.    ADVANTAGE - The underwater sludge lifting device is flexible and convenient, and has good sludge extracting suction effect, simple structure, good sealing, simple operation and good reliability.    DETAILED DESCRIPTION - An underwater sludge lifting device comprises two parallel boat floaters on water surface and crossing bridge type support which are integrally connected to form I-shape, 7-shaped drainage cylinder which is fixed below central section of bridge type support, propeller which is provided on central line of vertical section of drainage cylinder, driving shaft of propeller which is driven by motor on bridge type support after passing through top of suction cylinder, straight suction cylinder which is arranged at lower side of drainage cylinder, shaft which is arranged into through hole, and port which is in contact with surface of underwater sludge. The cross section of drainage cylinder is deployed in length direction of boat type floater. The end part of cross section is opening end. The opening is located below water surface and adjacent to water surface. The vertical section of drainage cylinder is protruded underwater. The side walls of drainage cylinder and suction cylinder are connected. The corresponding positions of contact surfaces are respectively provided with through holes in which elastic seal rings are arranged. The inner cavities of drainage cylinder and suction cylinder are communicated and separated from external water. The two ends of shaft are arranged on side walls of drainage cylinder and suction cylinder in water sealing way. The lower end of suction cylinder is drooped. The lower end of port can rotate around shaft.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the underwater sludge lifting device.    Reversing gear box (11)    First section of straight pipe (1401)    End section of straight pipe (1402)    Middle section of straight pipe (1403)