A fan biasing transmission mechanism includes a housing having first, second and third mounting chambers, a control rod mounted in the first mounting chamber, a driving gear wheel and a driven gear mounted on the control rod, a worm coupled to a motor and meshed with the driving gear wheel, a follower gear wheel pivotally mounted in the second mounting chamber, a link coupled with the follower gear wheel, a cap covering the housing, and two speed-changing transmission gears pivotally mounted in the third mounting chamber in a stepped manner and respectively meshed with the driven gear and the follower gear wheel.