Dipe cutting by Double Punching is an ideal and efficient method.On the basis of Scrap Out Going,the theoretical curve of the punch is deduced.According to the curve,the front of the punch is too slender and fracture easily in cutting.Double punching Method cut a slot on one side of the pipe first,then punch into the slot and cut off the pipe.High quality of the pipe end is obtained and the life of the punch is prolonged by this method.The shape of the punch is also clesigned on the basis of the mechanical analysis.