Abstract: In order to avoid obstacles in task space, overcome interior singularities and improve the performance of manipulators, redundant manipulators have been thoroughly researched and developed. In the process of designing BUAA-RR 7 degrees of freedom, a complete set of principles and methods are proposed on design of mechanical structure, joint and parts. BUAA-RR 7-DOF manipulator is characterized by self-motion and overcoming joint limitations, which has a feasible and compact structure. BUAA-RR operates dexterously and reliably, and is able to avoid obstacles and overcome singularity. Practice verifies the feasibility of above principles and methods.