The present invention relates to a method of controlling a heat-dissipating fan of a computer device, which is provided with a heat-dissipating fan, a controller, a first sensor unit, and a second sensor unit. The method of the present invention includes the following steps. First, the controller accepts a first signal and a second signal and controls the rotating speed of the heat-dissipating fan according to the first signal. Subsequently, the controller determines the first signal and the second signal. Next, the controller reduces the rotating speed of the heat-dissipating fan corresponding to the first signal to temporarily maintain the rotating speed at a constant to thereby reduce a noise value produced by the heat-dissipating fan.