Abstract: Because the interfering problem of the pitch-yaw motion coupling has been put forward and solved, the spherical gear with the complex and difficult process has to be used in the present flexible wrist in order to meet the special need of the pitch-yaw mechanism motion. The double-ring uncoupling principle in this article can solve the critical problem of the pitch-yaw-roll flexible wrist without the spherical gear drive, so we adopt the straight and cylinder gear driving method, without special process, which avoids the problem of the spherical gear driving complexity and processing difficulty. In addition, the flexible wrist has also the reference value in the designed aspect of the robot flexible arm.