Abstract: A water plug for an ornamental water ball to prevent from leak upon the water being frozen into ice; the water ball has a neck part mounted with a water plug; the water plug includes a flat plate and a buffer cylinder; the buffer cylinder has a round cylinder extended down from the center of the flat plate; the inside of the round cylinder is furnished with a semi-spherical membrane extended upwards; the water filled in the glass balls subject to being frozen into ice in winter; in that case, the ice therein would distend to need more space, and then the buffer space furnished in the buffer cylinder will meet the requirement so as to prevent the water ball from having water leak.