A power factor correction circuit, comprising: a power meter configured to measure a total harmonic distortion (THD) at an input port; a switching-type regulator that is controllable by a switch control signal in order to adjust a power factor; a controller configured to generate the switch control signal to control the switching-type regulator to perform power factor correction by controlling the on-time of the main switch of the switching-type regulator in a closed-loop control manner, wherein the main switch is turned on when it is detected that the inductor current crosses zero; wherein the controller is configured to inversely superimpose at least one predetermined harmonic component on a control signal for controlling an on-time of a main switch of the switching-type regulator to adjust the on-time, to decrease the THD; wherein the power meter is further configured to measure an amplitude ratio (Hn) of each harmonic component at the input port, and the controller is configured to set the amplitude ratio of each of the predetermined harmonic components based on a measured amplitude ratio of a corresponding harmonic component, and, in a predetermined order of the predetermined harmonic components and for each predetermined harmonic component, to adjust a phase of the predetermined harmonic component based on the measured THD until the measured THD is no longer decreased, wherein either the phase of each of the predetermined harmonic components is adjusted to progressively increase from zero until the measured THD is no longer decreased, or phase partition is performed, and a phase range where the phase of each of the predetermined harmonic components is located is determined, the phase of each of the predetermined harmonic components is adjusted within the phase range until the measured THD is no longer decreased. a power meter configured to measure a total harmonic distortion (THD) at an input port; a switching-type regulator that is controllable by a switch control signal in order to adjust a power factor; a controller configured to generate the switch control signal to control the switching-type regulator to perform power factor correction by controlling the on-time of the main switch of the switching-type regulator in a closed-loop control manner, wherein the main switch is turned on when it is detected that the inductor current crosses zero; wherein the controller is configured to inversely superimpose at least one predetermined harmonic component on a control signal for controlling an on-time of a main switch of the switching-type regulator to adjust the on-time, to decrease the THD; wherein the power meter is further configured to measure an amplitude ratio (Hn) of each harmonic component at the input port, and the controller is configured to set the amplitude ratio of each of the predetermined harmonic components based on a measured amplitude ratio of a corresponding harmonic component, and, in a predetermined order of the predetermined harmonic components and for each predetermined harmonic component, to adjust a phase of the predetermined harmonic component based on the measured THD until the measured THD is no longer decreased, wherein either the phase of each of the predetermined harmonic components is adjusted to progressively increase from zero until the measured THD is no longer decreased, or phase partition is performed, and a phase range where the phase of each of the predetermined harmonic components is located is determined, the phase of each of the predetermined harmonic components is adjusted within the phase range until the measured THD is no longer decreased. <EOS>