The invention discloses a movable-electrode electro-osmosis dewatering device for dewatering urban sewage sludge. The device consists of a polyvinyl chloride (PVC) sample loading barrel, a screw rod, a movable electrode group, an adjustable voltage direct current power supply and the like, wherein an alloy fixing electrode plate is arranged at the bottom of the sample loading barrel; the movable electrode group consisting of a stainless steel conducting rod, a pointed alloy electrode, an organic glass upper plate and a nut is rotatably connected with the screw rod in the center of the sample loading barrel; and after the sludge is charged into the sample loading barrel and the power is switched on, the screw rod is rotated at a fixed rotating speed to lower the movable electrode group at a constant speed, voltage is adjusted synchronously and voltage gradient between electrodes is kept so as to perform electro-osmosis dewatering. The problems of the reduction in the water content of adewatered sample, the rise of resistance, the increase of consumed voltage and the reduction in electro-osmosis efficiency in a fixed electrode electro-osmosis treatment method can be solved. The water content of discharged sludge of which the water content is 80 percent and voltage and electrode moving rate are selected according to an electro-osmosis characteristic can be lowered to be between 60 and 70 percent after treatment and the energy consumption on the treatment of each square meter of wet sludge is about 120 kilowatt hours.