The invention discloses a spiral extrusion type sludge dewaterer comprising a frame (1), a water inlet part, an sludge outlet part (41), an water outlet part, a screw axis (2) and filter disc groups formed by the crossover interval arrangement of a plurality of annular static filter discs (5) and annular dynamic filter discs (6), wherein, each static filter disc (5) is fixed relatively to the frame (1), each dynamic filter disc (6) can form upper and lower spacing swinging movement relative to the frame (1) following the screw axis (2) under the driving of a transmission mechanism, and besides, the distance between the adjacent two static filter discs (5) is a little bigger than the thickness of the dynamic filter disc (6) so as to form a clearance (7) for water to flow through between the static filter discs (5) and dynamic filter discs (6). Compared with the prior art, the effluent water directly flows out from the clearances between filter disc groups, thus avoiding the abrasive action of sludge to the static filter discs and dynamic filter discs; and the device is long in service time, can realize solid-liquid separation by using only one power supply, and is low in energy consumption, and the parts is convenient to arrange, simple in structure and easy to practically implement.