The invention discloses a sludge dewatering device for sewage treatment, belonging to the field of sewage treatment technology. The sludge dewatering device provided by the invention comprises a base body, a bearing plate, first filter cloth, a first motor, a first rotating body, second filter cloth, brushing hair, a sealing ring, an antifouling membrane, a plurality of linear actuators, a pedestal, a second motor, a second rotating body, a first extruding body, a plurality of first electric push rods, a second extruding body, a water-absorbing sponge, a water-receiving tank, a water-receiving pipeline, a sludge pump, a sludge conveying pipe, a valve, a reset spring, a sludge drum and a control module. The sludge dewatering device for sewage treatment in the embodiments of the invention realizes the dewatering treatment of sludge and allows the treated sludge to be small in size; the sludge dewatering device realizes sludge reduction treatment; and the movement of every executive components is controlled by a control module, so automatic sludge dewatering is realized, and high treatment efficiency is obtained.