This invention relates to a three-phase square-wave permanent magnet brushless DC motor for solving problems of the existing square-wave permanent Magnet Motor and sine-wave permanent magnet motor. In this invention, the number 2P of magnetic poles on the said rotor core is 8; the slot number Z of the said stator core is 12, accordingly there are 12 teeth, including three big teeth, three medium teeth and six small teeth; the ratio of their mechanical angles is 50° (±5°) for big teeth: 40° (±5°) for medium teeth: 15° (±5°) for small teeth, and the sum of the mechanical angles of one big tooth, one medium tooth and two small teeth must be 120°. Three-phase concentrated windings are respectively wound on the big teeth and the medium teeth, in which there are only two concentrated windings for each phase, thus there are only 6 concentrated windings for the three-phase motor. With driven by three-phase square-wave current, the said motor can produce a smooth torque which ripple index corresponds to that of the sine-wave permanent magnet servo motor, at the same time, it also has a plurality of advantages including windings end minimization, air-gap minimization, material minimization, cogging torque minimization and loss minimization and so on.