Profile milling flying saw is one of the most advanced flying saws in the modern world, its tracking system driven by servo motor and its sawing system using profile milling method. This flying saw has many advantages, such as simple control system, less jamming signal, higher dimensional accuracy, flat section and convenient operation. Since the profile milling flying saw was launched, it has been put into a wide applications. The paper gives a brief introduction of the working principles of tracking system and makes a specific analysis of its motion. The movement patterns of saw cutting round pipes and square pipes are given in the sawing system and the mathematical models of saw cutting square pipes are established by analysis. In fact, the methods mentioned above have been used in practice. The dimensional accuracy of sawing welded pipe has reached the requirements of British BS standards and come up to the world advanced level.