The invention discloses device and method for cell wall breaking in a municipal sludge dewatering process. The device comprises an adjusting pond, a stirrer, a hot water tank, a hot water pump, a hot water pipe which is communicated with the adjusting pond through a heat exchanger, a sludge pump, a valve, a sludge inlet pipe which is communicated with the adjusting pond through the heat exchanger, an alkaline liquid tank, an alkaline liquid pump, an alkaline liquid pipe which is communicated with the adjusting pond, and a dewatering machine which is connected with the adjusting pond, wherein the filtrate from the dewatering machine is discharged through the heat exchanger, and the adjusting pond is provided with an alkaline liquid concentration sensor, a temperature sensor and a controller and is in connected connection with the sludge pump, a water pump, the alkaline liquid pump, the motor of the stirrer, the dewatering machine and the valve. The cell wall breaking method comprises the following steps of: (1) performing a pretest; (2) preparing an alkaline liquid; (3) loading sludge to the adjusting pond in which the sludge is preheated; (4) adding alkali to adjust the pH of the sludge and allowing mixed reactions to take place; (5) starting the dewatering machine and a filtrate return device; (6) detecting the sludge mixed reaction results at a preset time, to ensure optimum wall-breaking dewatering effect of the sludge; and (7) repeating from the step (3) to the step (6). The device and method provided by the invention are applied to the wall-breaking treatment prior to the dewatering treatment of the sludge, has a perfect structure, is easy to operate, and improves effects.