Coupling is used for the connection of different organizations in the two axis (the driving shaft and the driven shaft)of mechanical parts to rotate together to transfer torque. Overloaded power transmission at high speed, some couplings and buffering, vibration and improve the dynamic performance of the shaft. Coupling consists of two parts, connected with the driving shaft and the driven shaft. Most of the general power machine by means ofcoupling machine connected with work. The coupling of various kinds, according to the relative position and location changes are connected with two axis, can be divided into: fixed coupling. Mainly used in the two axis in a strict and no relative displacement in the work place, the general structure is relatively simple, easy to manufacture, and two instantaneous speed is the same, the main flange coupling, sleeve coupling, clamp couplingetc.. The transferable type couplings. Mainly used in the two axis deflection or relative displacement in the work place, according to the method to compensate the displacement can be divided into rigid movable elastic couplingand movable type coupling. Rigid movable coupling by using the dynamic coupling between parts of a work is connected with a certain direction or direction of the activities of compensation, such as jaw couplings (permissible axial displacement), cross slot coupling (for connecting parallel shafts displacement or angular displacement is very small), universal coupling (for two large deflection angle or in the work place is angular displacement), gear couplings (allow comprehensive displacement), chain couplings (allowing the radial displacement), elastic movabletype coupling (referred to as the elastic coupling) using the elastic deformation of the elastic element tocompensate the deflection and displacement of the elastic element, at the same time also has the buffering and damping performance, such as serpentine spring coupling, coupling, multi leaf spring elastic ring radial pin coupling, nylon pin coupling, coupling with rubber sleeve etc.. The coupling bit has been standardized. When the choice should be selected according to the type of work requirements, and in accordance with the diameter of the shaft torque and speed calculation, and then from the manual found suitable model, finally the necessarycalculation of some key parts. The classification of ball universal coupling comprises conical bowl spring coupling SWP, SWC type cross shaft universal coupling.