Coupling according to different work condition, should possess the following properties: 1. Can be moved. Can compensate relative displacement ability, two rotary components to be connected component between the manufacture and installation error, the operation temperature variation, and the load deformation, are required to have certain can be moved. Movable property compensation or relief, is caused by the relative displacement between the rotary component of shaft, bearing, coupling and other parts of the additional load. 2. Buffer. Often used to load the occasion of starting or working load changes, the vibration and has the buffer, and can protect the prime mover and work machine, in order to avoid damage. 3. Safe, reliable, have enough strength and service life. 4. Structure is simple, maintenance is convenient. This is the performance of the coupling is required.