The invention provides an automatic power control circuit and a method. The control circuit can be applied for controlling a laser generation module. The laser generation module is provided with a laser generator used for generating the laser and a photoreceptor used for outputting the detection result corresponding to the power of the laser. The automatic power control circuit is provided with acomparator which is coupled with the photoreceptor and is biased by a first voltage level and used for comparing the detection result with the reference signal so as to generate the comparison result,a level positioner which is coupled with the comparator and used for moving a middle voltage level which is controlled by the comparison result so as to generate control voltage and a driver which iscoupled with the level positioner and the laser generator and used for driving the laser generator according to the control voltage and a second voltage level. The automatic power control circuit canincrease the linear range of the voltage level and leads the circuit operating in the low voltage domain and the circuit operating in the high voltage domain to be successfully connected and ensuresthe integral operation to be clear.