Heat dissipation fan with magnet ring of varying thickness

A heat dissipation fan comprising:

• a housing comprising a top plate defining an air inlet therein and a bottom plate defining an air outlet therein;
• a stator received in the housing and comprising a stator core;
• and
• a rotor rotatable around the stator, the rotor comprising a hub and a magnet ring received in the hub and surrounding the stator, the hub comprising a top wall located at the air inlet, a shaft extending downwardly from a center of the top wall towards the air outlet and a side wall extending downwardly from a periphery of the top wall, the magnet ring having a larger radial thickness at a first end which is adjacent to the air outlet than at a second end which is adjacent to the air inlet, such that an attracting force formed between the first end of the magnet ring and the stator core is larger than that formed between the second end of the magnet ring and the stator core.