The invention discloses a low-speed totally-closed type double-permanent-magnet single-phase brushless synchronous generator. The generator comprises a totally-closed sealed cavity and an outer air path containing cavity, wherein the totally-closed sealed cavity is formed inside a case in an enclosed mode, and the outer air path containing cavity is formed outside the case in an enclosed mode. A rotating shaft is arranged in the sealed cavity, and the two ends of the rotating shaft extend out of the two ends of the case. A main generator and compensated generator combined stator, a permanent-magnet exciter stator, a permanent-magnet main generator rotor, a compensated generator rotor, a permanent-magnet exciter armature rotor and an inner fan are arranged in the sealed cavity. A plurality of ventilation hole grooves are punched in the outer circle of a stator lamination of the combined stator inwards, and then the ventilation hole grooves and the inner fan form inner heat dissipation air path channels; a plurality of ventilation hole grooves are punched in the outer circle of a stator lamination of the permanent-magnet exciter stator inwards, and then the ventilation hole grooves and the inner fan form inner heat dissipation air path channels; a stator spacer for stator winding is formed between every two adjacent ventilation hole grooves. A rotation AVR, a voltage signal rotation sensor and an outer fan are arranged in the outer air path containing cavity. Due to the design of the special ventilation hole grooves in the stator laminations and the reasonable inner and outer air paths of the whole generator, the totally-closed type design of the generator can be achieved.