The invention discloses a speed regulation control circuit of a pulse-width-modulation computer cooling fan. The speed regulation control circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first capacitor, a second capacitor, a first potentiometer, a second potentiometer, a first comparator, a second comparator, a third comparator, a thermistor, a light-emitting diode, an audion, a multivibrator and the fan. The speed regulating control circuit of the pulse-width-modulation computer cooling fan is a control circuit achieving automatic speed regulating through a pulse-width-modulation cooling fan motor, and the speed of the fan can be automatically regulated according to the temperature inside an instrument; the same-phase input end of the first comparator is connected with the thermistor; and when the potential of the same-phase input end of the first comparator drops due to temperature rising, the output voltage of the first comparator also drops, the duty ratio of the output waveform of the second comparator is improved, and the rotating speed of the fan is increased through the audion.