The invention relates to a pulsator washing machine and a vibration control method thereof. Particularly, the invention provides a vibration control method of a pulsator washing machine. The pulsator washing machine comprises a housing, an outer roller mounted in the housing and an inner roller rotatably supported in the outer roller. The outer roller is supported in the housing by a magnetorheological damper. The magnetorheological damper is configured to be controlled to generate damping inversely proportional to the rotation speed of the inner roller in the spin-dry process of the pulsator washing machine so as to control the vibration of the outer roller. The vibration control method comprises the steps that the rotation speed of the inner roller is obtained in real time during the spin-dry process of the pulsator washing machine; the damping of the magnetorheological damper is adjusted in real time according to the rotation speed of the inner roller to be reversely proportional to the rotation speed of the inner roller so as to control the vibration of the outer roller. The pulsator washing machine and the vibration control method thereof are capable of increasing or decreasing the damping in a targeted way, reducing or avoiding the vibration of the outer roller, and consequently avoiding the sympathetic vibration of the whole pulsator washing machine caused by the vibration of the outer roller.