A rotary flange comprises an upper sealing seat and a bush ring, wherein the upper sealing seat and the bush ring are fixedly arranged on a main steel tube; threads are arranged on the periphery of the bush ring; an adjusting screw is arranged on the threads of the periphery of the bush ring in a matched manner; a mounting seat is arranged between the upper sealing seat and the adjusting nut; a plurality of steel balls are arranged in steel ball running tracks; an upper sealing ring and a lower sealing ring are respectively arranged at the upper end and the lower end of the mounting seat; an upper sealing groove is formed in the periphery of the upper sealing seat; a lower sealing groove is formed in the periphery of the adjusting nut; and two sealing hoops are respectively arranged in the upper sealing groove and the lower sealing groove and are respectively matched with the inner wall of the upper sealing ring and the inner wall of the lower sealing ring. The sealing hoops are arranged on the upper sealing seat and the bush ring, underground water, mud and sand and gravel particles are prevented from entering a rotating gap by using an oil storage cavity, and a phenomenon that a rotating component is jammed and is severely worn is avoided. The steel ball running tracks and the steel balls are respectively arranged between the upper sealing seat and the mounting seat and between the bush ring and the mounting seat, so that the mounting seat rotates flexibly.