High speed water jet special machining utilizes the beam of water with very high dynamic energy to cut materials,therefore it actually belongs to the machining tool of high energy beam.In many applications,water jet machining has some advantages over the laser,plasma and EDM etc.,such as less expensive,environmentally friendly and has no heat affected zone(working temperature less than 100℃).On the other hand,water jet machining is no contact with parts,flexible,reasonably precise,narrow kerf width,less waste of materials,no contamination,easy to integrate CNC to precisely cut any materials with complicated shapes.Therefore water jet is a good unconventional tool for hard,fragile and very difficult to cut materials,e.g.composite,concrete,ceramics and stone materials etc.