Series-parallel planetary reducer

The utility model provides a series-parallel planetary speed reducer. The speed reducer is characterized in that the input shaft, the intermediate shaft and the output shaft are located on the same center line; an input shaft gear in the ordinary gear train is meshed with a transition shaft primary gear; the transition shaft is a gear shaft, a gear part on the transition shaft is meshed with an intermediate shaft gear, the intermediate shaft is a gear shaft, a gear part of the intermediate shaft is a sun gear in an epicyclic gear train, the sun gear is meshed with planet gears, the planet gears are large in gear width and meshed with a left inner gear ring and a right inner gear ring at the same time, the left inner gear ring is fixed, and the right inner gear ring rotates. The rotating right inner gear ring is connected with the output shaft through a bolt; the transmission system has the advantages of being novel in structure, high in power density, high in bearing capacity, long inservice life and capable