A fan central tube coupling structure includes a base and a central tube. The base has a first section and a second section that together define an upward tapered receiving recess below the base. The central tube is externally provided on around a bottom end with a first and a second protruded section and an engagement groove defined between the first and second protruded sections. The second protruded section has an interference pressing surface defined on an outermost peripheral surface thereof. The central tube is axially extended through the base, such that the second protruded section is axially press-fitted into the tapered receiving recess and the interference pressing surface is radially outward forced against the tapered receiving recess. In the meantime, the second section of the base is fitted in the engagement groove and clamped in place by between the first protruded section and the second protruded section.