The invention relates to the field of bridge construction, in particular to a pier-top rotator structure of a bridge. The pier-top rotator structure comprises rotator driving devices, lifting devices, supports and a pier of the bridge. A rotator spherical hinge is arranged on the top of the pier, and a steel pile casing is arranged on the outer side of the circumference of an upper spherical hinge of the rotator spherical hinge, so that local compression of a beam bottom meets the stress requirement, pier-top operation space is increased, and the safety performance is improved. In addition, the upper spherical hinge and the steel pile casing are also used as transverse anti-drop beam facilities after a rotator is constructed. The invention further relates to a method for constructing the pier-top rotator of the bridge. The method include steps of pouring the pier of the bridge and arranging the rotator spherical hinge on the top of the pier; pouring a beam; arranging the rotator driving devices and the lifting devices; connecting the rotator driving devices with a turntable, enabling the turntable to rotate under the effect of acting force of the rotator driving devices and driving the beam to rotate; lifting the beam by the lifting devices and enabling space at the bottom of the beam to meet installation requirements of the supports; connecting the supports to the beam; and detaching the rotator driving devices and the lifting devices. The pier-top rotator structure and the method have the advantages that the method is safe and reliable, the cost is low, and operation is easy and convenient.