The invention discloses a single-core brushless synchronous motor. A stator consists of a stator core, a stator single-phase AC excitation winding and a stator three-phase power winding; a rotor consists of a rotor core, a rotor AC induction winding and a rotor DC exciting winding; both the stator core and the rotor core have a single-core structure; the rotor has an invisible-magnetic-pole structure; the inside of the stator core is provided with a short-pitch three-phase power winding arrayed in a distributive manner and an integral-pitch single-phase AC exciting winding arrayed in a centralized manner, and the short-pitch three-phase power winding and the single-phase AC exciting winding are arranged in a big stator slot and a small stator slot respectively; the three-phase power winding is externally connected with a power source, and the single-phase AC excitation winding is externally connected with an intermediate-frequency power source; the inside of the rotor core is providedwith a DC exciting winding arrayed concentrically and an AC induction winding arrayed in a distributive manner, and the DC exciting winding and the AC induction winding are arranged in a big rotor slot and a small rotor slot respectively; and a rotary rectifier is fixed on a rotor shaft. The single-core brushless synchronous motor gets rid of a separate exciting motor which is in coaxial connection in the conventional brushless synchronous motor, so that the single-core brushless synchronous motor has simple structure, reliable operation, convenient maintenance, high efficiency and wide practicability.