Centrifugal fan structure

The utility model discloses a centrifugal fan structure which comprises a bottom plate, a cover plate and an impeller arranged between the cover plate and the bottom plate, a side wall plate is arranged between the edge of the bottom plate and the cover plate, an air supply outlet is formed in one side of the side wall plate, and an air inlet is formed in the cover plate. The impeller comprises a hub; an annular step is arranged on the top surface of the hub, and a plurality of blades which are uniformly distributed around the step in the circumferential direction are arranged on the step; each blade comprises an arc-shaped connecting section and an arc-shaped extending section; a vertical part is downwards arranged in the middle of the extending section, the bottom end of the vertical part is connected with a horizontal part, the horizontal part extends to the free end of the extending section in the direction of the extending section, and a receding opening is formed between the vertical part and the horizo