Cleaning particles are arranged in a space between the inner tub and the outer tub of a washing machine. A drainage and dewatering control method comprises: opening a drainage valve; determining the amount of the cleaning particles per each unit volume of water in the space; and controlling the rotating speed of the inner tub. Drainage and dewatering processes are divided into at least two control stages according to the amount of the cleaning particles per each unit volume of water in the space, different rotating ways of the inner tub are set in respective stages, and the rotating speed of the inner tub is higher in the stage that the amount of the cleaning particles per unit volume of water is larger. A control stage is selected according to the detected amount of the cleaning particles per unit volume of water in the space.
