Abstract: This disclosure discloses a heat dissipating system using fans for an electronic device. The electronic device includes a first air outlet and a second air outlet. The heat dissipating system using fans includes a processor, a first fan, a second fan, an orientation sensor, and a temperature sensor. The orientation sensor is for sensing whether the electronic device is under a horizontal state or a vertical state and generating a corresponding orientation signal. The temperature sensor is for sensing the temperature of the electronic device and generating a temperature signal. When the temperature signal is greater than or equal to a predetermined value, the processor activates the first fan and the second fan. When the temperature signal is less than the predetermined value, the processor selectively activates one of the first fan and the second fan according to handedness information and the orientation signal.