The invention discloses an electroosmosis and mechanical filter-pressing coupled sewage sludge dewatering method which comprises the following steps: (1) a primary mechanical filter-pressing dewatering stage: the sewage sludge enters a primary filter-pressing dewatering device, and the primary mechanical filter-pressing dewatering is realized in the primary filter-pressing dewatering device; (2) an electroosmosis and mechanical filter-pressing coupled dewatering stage: the anode plate and cathode plate of electroosmosis are arranged in a coupled dewatering cylinder, and a direct-current power supply supplies power to the anode plate and cathode plate of electroosmosis, the anode plate and cathode plate form a press-filtering cavity with the coupled dewatering cylinder, and mechanical filter-pressing between the anode plate and cathode plate is maintained while electroosmosis dewatering is realized; and (3) a high-pressure mechanical filter-pressing dewatering stage: the sludge water content of the anode plate is low; and at the moment, the direct-current power supply is cut off, the electroosmosis dewatering is stopped, and pressure between the anode plate and cathode is increased to realize high-pressure mechanical filter-pressing dewatering. By adopting the method disclosed by the invention, the sludge resistance of the anode layer is increased slowly, the dewatering effect is good, and the water content in the sludge thickness direction is in uniform distribution.