A power factor correction conversion device and control method thereof are adapted to send an AC signal to a power factor correction conversion device, convert the AC signal into a DC signal, and perform power factor correction of the DC signal, so as to change a power factor sent to a back-end load, wherein the control method includes a rectification step, a feedback step, a ripple calculating step, a ripple offsetting step, a logical computation step, a pulse width modulation step and a power factor correcting step. Hence, the second-order ripple component in a feedback signal is eliminated to thereby increase the response speed of the power factor correction conversion device and reduce the distortion rate of the current, thus increasing the power factor sent to the back-end load.