The invention relates to a household abnormal water-usage mechanical automatic valve closing method. It comprises a frame which has a water chamber, and a blade wheel inside the water chamber that impacted by water to rotate positively. The blade wheel via transmission device is connected to the speed reducer, to transmit the positive rotational to the output axle of speed reducer; said output axle is connected to the control valve. The invention is characterized in that: when in normal water usage, the trigger element in the control valve is in the turning-on section of valve; when the abnormal water-usage, the water is large, the trigger element will rotate to the same direction and depart away the turning-on section to automatically close the valve. |