The invention relates to a power factor correction circuit of a power converter, which is coupled with the power converter for regulating the power factor of the power converter. The power factor is corrected by the following steps that: a voltage feedback circuit generates a voltage command signal according to an output signal of the power converter; a computing circuit receives a voltage input signal, a current sensing signal and a voltage command signal of the power converter, generates a multiplication signal according to the voltage input signal and the voltage command signal, generates a first reference signal according to the voltage input signal and the current sensing signal and generates a control signal according to the multiplication signal and the first reference signal; and a switching circuit generates a first switching signal according to the control signal and a second reference signal for switching a switch of the power converter. Thus, in the invention, a multiplier instead of a divider is adopted, so the structure of the power factor correction circuit is simple, the volume of the power factor correction circuit is reduced as much as possible, and cost is reduced.