The invention proposes a flywheel-type motor for a diesel engine. The flywheel-type motor comprises a crank shaft, excitation windings, a stator iron core, armature windings and a rotor iron core, wherein 2N rotor poles with circular fan-shaped bulges are arranged on the inner side end surface of a round disc of the rotor iron core, 3N stator poles with circular fan-shaped bulges are uniformly arranged on the end surface, opposite to the end surface of each stator pole, of the stator iron core, the stator iron core is provided with a groove among each three stator poles, the excitation coil is wound in the groove and wound around the three stator poles, the winding directions of adjacent excitation coils are opposite, each stator pole is provided with the one of the armature coils wound around an axial direction, an armature winding is divided into three phases, and each phase of the armature coil comprises the same-phase armature coil. By the flywheel-type motor, the size of a gap magnetic field is adjusted by adjusting the size of an excitation current, and thus, stable output voltage can be maintained on the condition of variable load and variable rotational speed of the motor.