An air conditioning system includes a control unit, a circulation system, an AC-to-DC conversion unit, and a fan module. The control unit detects an area temperature, controls the compressor unit being in operation or not in operation according to the area temperature and a setting temperature set by the control unit, and control a rotation speed of the condensing fan according to a temperature difference between the area temperature and the setting temperature. When the area temperature is greater than the setting temperature, the control unit controls the compressor unit being in operation and control the condensing fan being in full-speed operation.