An illumination system including a master control unit, a device unit, a driving circuit unit, and an illumination unit is provided. The master control unit receives an input signal and outputs a control signal by performing a program operation processing to the input signal. The device unit analyzes the control signal so as to obtain a color temperature setting value and a brightness setting value, and generates two output signals according to the brightness setting value and two color temperature adjusting signals determined by the color temperature setting value. The illumination unit has at least two lamps with different color temperatures. The driving circuit unit receives and converts the two output signals so as to proportionally output two driving signals to respectively drive the two lamps. One of the two output signals is enabled after the other of the two output signals is disabled for a predetermined time.