A brushless direct current electric motor includes a first sub-motor and a second sub-motor. The first sub-motor and the second sub-motor share a common rotor, and each comprises an independent stator. The stators of each sub-motor comprises a plurality of teeth and a plurality of windings. The teeth of the first sub-motor and the teeth of the second sub-motor are interleavingly arranged in a circumferential direction or arranged side by side in an axial direction. The first sub-motor and the second sub-motor are configured to cooperatively work as a single electric motor to output a normal power. When one of the sub-motors breaks down, the other sub-motor can be operated independently to enhance reliability and safety of the brushless direct current electric motor.