Outer-rotor permanent magnet brushless motor

An outer-rotor permanent magnet brushless motor is disclosed, which comprises an outer-rotor and an inner-stator. The outer-rotor configured with P poles, P is a natural number and denotes a multiple of 4. The inner-stator has a stator axle, and S teeth which configured on outer surface of stator, S=P1, S is a natural number. Each teeth configured with a boost part which has an outer surface facing the outer-rotor. A circle is formed about a center of the stator axle from the center of the outer surface. A correction angle a1 and an original angle is defined from the center of the outer surface. The outer surface is composed with a first arc surface, and two second arc surfaces that connected to the opposite ends of the first arc surface. The first arc surface is within a coverage of the correction angle a1. The second arc surfaces are away the circle toward to the stator axle from the position that the second arc surfaces are connected to the first arc surface. The width of the boost part is within a coverag