A brushless DC motor including a casing, a stator assembly, a rotor assembly, a magnetic ring, and a circuit board with a Hall element. The stator assembly mounted in the casing and includes a stator core, a coil winding, and an end insulation plate. The rotor assembly includes a rotor core and a permanent magnet, and the end surface of the rotor core is coupled to a magnetic ring support. A convex support ring spaced apart from the permanent magnet is mounted on the edge of the magnetic ring support. The top of the convex support ring is sheathed with the magnetic ring and the Hall element extending out of the circuit board is located on the side of the magnetic ring. The motor minimizes the interference of the magnetic tile and improves measuring accuracy of the Hall element, all while having a simple structure, convenient mounting, and low costs.