A coaxial multi-degree-of-freedom (multi-DOF) single motor with its topology and structure design method is disclosed in the present invention. A single stator with one set of concentrated windings is adopted, and the winding configuration is designed based on the required control DOFs through a variable slot pitch angle method. The rotor part adopts the hybrid-embedded structure and the coaxial-nested shafts, such that the multi-rotor operation within a single motor is realized. The parameters of the rotor part are configured according to the parameters of the stator part and the winding configuration. In this design, rotating magnetic fields with different pole-pair numbers are generated by a common set of stator windings. Decoupled control and multi-DOF operation of multiple rotors are achieved in a single machine. Furthermore, the split-tooth structure is added to introduce the flux modulation effect in the air-gap magnetic field.