The current wave form of active boost PFC is simulated in time domain and frequency domain. With the voltage of 220 v, the inductance of 15 mH, the capacitance of 5040 μF, the load of 2500 W, the integrated power factor, fundamental power factor, and distortion are analyzed. The distortion is enhanced with the increase of frequency. Comparing high-order harmonic part under 10 mH and 15 Mh, it is demonstrated that the appropriate OFF phase angle changes with different requirement: the angle is 37 degree with distortion in least while the one is 34 degree with maximum integrated power factor. Topology and results are proposed. The results demonstrate that the power factor of real PFC circuit is up to 0.975.