The present invention relates to a circuit and method for optimizing an input voltage range of an IC chip. In the circuit, a pull-up unit, receives an input voltage and then outputs a corresponding voltage level; a trigger unit compares the voltage level output by the pull-up unit with a given threshold voltage, and outputs an enabling signal of corresponding level to an enabling end of the IC chip based on the comparison result, so as to control the IC chip to start/stop; and a voltage stabilizing unit receives the voltage levels output by the pull-up unit and the trigger unit, and then outputs a voltage of corresponding level to the pull-up unit based on the voltage levels output by the pull-up unit and the trigger unit, so that the voltage level output by the pull-up unit is higher than or equal to the threshold voltage and thereby the IC chip starts operation, or so that the voltage level output by the pull-up unit is maintained to be higher than or equal to the threshold voltage and thereby the operation of the IC chip is not affected by variations of the input voltage. The present invention can ensure that when the input voltage is changed within a certain range the IC still can work in a normal manner.