A centrifugal fan with a permanent-magnet brush-less motor system is provided with a volute, an outer rotor motor installed in the volute through a bracket, and an impeller externally sleeved on the outer rotor motor and positioned in the volute. The impeller is connected with the outer rotor motor and consists of a volute board and side boards on two sides of the volute board. The volute board is formed with an opening at a part on the horizontal plane and a bridge arch-type radiator having radiating fins matched with the opening is installed at the opening. The centrifugal fan improves heat dissipation with load changes allowing the driver to operate at lower temperatures that improves operating efficiency and service life. The larger the load, the better the heat dissipation effect of the driver.