A heat dissipation fan used in a frame server, includes a rotation axis and a plurality of fan blades. The rotation axis is composed of a main portion and an extension portion, and the diameter of the main portion is greater than that of the extension portion. The fan blades extend outward from the rotation axis, and are utilized to drive the wind from one side of the rotation axis to the other side of the rotation axis in a direction perpendicular to the rotation axis. As such, greatly increase the air cutting area of the fan blades. In this manner, in the server frame studded with electronic devices and having very limited heat dissipation space, the heat dissipation efficiency of the server can be raised significantly, so that the electronic devices may function normally and efficiently.