Provided is a fault diagnosis method and device for an engine switch type water pump. The method comprises the steps that whether an engine is in the warm operation state or not is judged; when the engine is in the warm operation state, according to the current working condition of the engine, the corresponding cooling liquid theoretical temperature value is calculated; the cooling liquid actual temperature value is obtained; and according to the relation between the change rate of the cooling liquid theoretical temperature value and the change rate of the cooling liquid actual temperature value and the difference value between the change rate of the cooling liquid theoretical temperature value and the change rate of the cooling liquid actual temperature value within the preset time quantum, whether the switch type water pump is stuck or not is judged. By the adoption of the method and device, whether the water pump is stuck or not can be detected in time.