A intelligent cascaded synchronous electric motor-generator tandem of cumulative compound excitation comprises at least a synchronous electric motor-generator tandem (namely MG tandem), a storage battery cluster and an autotransformer. Each MG tandem comprises at least a pair of motor and generator having a common stator and a common rotor shaft. The storage battery cluster, which provides a DC power to general loads and motor, serves as a DC power reservoir to be recharged by generator. The autotransformer serves to regulate the AC voltage output from generator via multiple output taps thereon for supplying various AC voltages to different external loads. By integrating all components aforesaid with common magnetic flux interacted mutually, upon being energized by DC power from storage battery cluster, the motor will transfer rotational torque to drive the generator in enhanced synergistic manner.