Vertical shaft fan

A draught fan sleeve and an air hole pipe are coaxially and fixedly connected to the bottom of a well lid from top to bottom in sequence, a plurality of ventilation holes are evenly formed in the range, corresponding to the interior of the draught fan sleeve, of the well lid, a motor box is coaxially and fixedly connected to the interior of the draught fan sleeve, and a driving motor is coaxially and fixedly connected to the interior of the motor box; the bottom end of a rotating shaft of the driving motor downwards extends out of the motor box and then is coaxially and fixedly connected with fan blades, ventilation openings are formed in the two opposite sides of the bottom of the side wall of the air hole pipe correspondingly, the bottom of the air hole pipe is a conical arc face inclining downwards in the direction from the axis to the edge, and the lower edges of the ventilation openings are flush with the conical arc face. The ventilation openings are distributed in a central symmetry mode with the axis