The invention discloses a water ecological restoration device, which comprises a main controller part, a power supply part, a motor driving part, a flow-dividing structure part, a buoy body and a sensor detection part. The invention provides a water ecological restoration system, which comprises a remote data center, the water ecological restoration device and a matched APP. The invention furtherdiscloses a water ecological restoration method. The water ecological restoration method specifically comprises the steps that thresholds and parameters for system operation are configured; a main controller receives an instruction of an upper computer and controls motor impellers to rotate; the impellers rotate to drive a water body to form a transverse flow and a longitudinal flow; the water ecological restoration device promotes exchanging of a shallow water body and a deep water body by generating transverse water circulation and longitudinal water circulation, layering of the water bodiesis eliminated, homogenization of the water bodies is promoted, and the dissolved oxygen content of the deep water body is increased significantly. According to the water ecological restoration device, system and method, a closed-loop control strategy is adopted, exchanging of the shallow water body and the deep water body is promoted by forming longitudinal water circulation and transverse watercirculation in the water bodies within the certain range, the dissolved oxygen content of the water bodies is increased, the water quality is improved, and water ecological restoration is achieved.