Abstract: Taking the existing connection problems into consideration, the co-authors analyze the causes for the inner cooling water pipe of the mandrel on the Accu-Roll mill located at Yantai Lubao Steel Tube Corp., Ltd.. The harmful effects on the water piping and flanges by the repeated tremble of the cooling water piping in the mandrel supporting section during rolling are removed by means of using 4-layer-cable high pressure rubber pipes to replace the original seamless steel pipes. In addition, the mandrel car and the water returning system are also partially modified in order to guarantee the product quality and reduce the mandrel consumption.