The decelerating motor has the advantages of long working life, simple maintenance and wide application. Its series can be divided into single-stage, two-stage and three-stage gear reduction motor, the installation of the main layout of the expansion, coaxial and shunt. In the expansion type of two-stage cylindrical decelerating motor, the position of the gears is asymmetric relative to the supporting position. When the shaft produces bending and torsion deformation, the load distribution in the tooth width is not uniform. Therefore, the shaft should be designed with larger stiffness, and the gear away from the input or output end. The position of the extension shaft of its shunt deceleration motor can be extended by any side, which is convenient for the overall configuration of the machine, should make one of the shaft can do a little axial swimming, so as not to jam the gear. The radial dimension of coaxial reducer motor is compact, but the axial dimension is large. Because of the larger middle shaft, the greater the disturbance of the shaft under load, so the load concentration along the tooth width is more serious. At the same time, because the center of the two gears must be the same, so the load-bearing capacity of the gear is difficult to make full use of, and in the middle part of the reduction bearing lubrication is more difficult.