On the basis of transmission principle and existing problems analysis of existing ring-reducer with small tooth number difference and parallel and movable axis, a new two-stage coaxial ring-reducer was put forward which constituted of a common cylindrical gear transmission and a double loop reduction transmission. The structural characteristics, transmission principle were analyzed. Based on these results, the model machine was designed and manufactured. The rigid body dynamics model of entire reducer transmission system was established by using ADAMS software. The force analysis of key force components-tumbler bearing was conducted. The load-carrying capacity of both inside and outside of meshing gears was calculated with finite element contacts analysis methods. Reducer performance was tested on test rig of gear transmission, which showed that the transmission efficiency of reducer was 94% and vibration was country B level. 