The end coupling is the main component of the aluminum hot rolling process. The end coupling used for transmission of rotational power with heavy-duty load. Fracture of the end coupling causes serious economic injury because an end coupling is a very expensive component and takes a long time to repair. To prevent the destruction of the end coupling it is essential for mechanical life cycle to be known. In this paper, a parameter study on end coupling was performed in order to minimize maximum stress of an end coupling under static loads. To verify the interference of spindle assembly with modified end coupling, kinematic simulation was performed by applying the various combination type and dynamic boundary condition of the spindle assembly. The interference of an optimized model did not occur during combination process and driving process. As a result of an optimum design for life extension on end coupling, the maximum stress of end coupling was reduced about 26% compared with original model.