The present invention relates to a power factor correction circuit and a driving method thereof.The power factor correction circuit includes: an inductor for receiving an input voltage and supplying output power; a power switch connected to the inductor to control an inductor current flowing through the inductor; an auxiliary conductor coupled to the inductor with a predetermined turn ratio; and a power factor correction controller that controls the output power by controlling the switching operation of the power switch and determines whether or not the output voltage of the output power is an over-voltage. The power factor correction controller generates an input peak voltage corresponding to the peak of the input voltage by using a clamping current for maintaining an auxiliary voltage, which is the both-end voltage of the auxiliary inductor, at a predetermined clamping voltage during the turn-on period of the power switch so as to prevent the auxiliary voltage from becoming a negative voltage, generates a duty voltage corresponding to the duty of the power switch, and determines whether or not the output voltage is an over-voltage according to a result of comparison between the input peak voltage and the duty voltage.