This paper proposed a boost power factor correction (PFC) controller with feedforward adaptive on-time control designed and fabricated using TSMC 2P4M 0.35μm CMOS process. With feedforward adaptive on-time control the proposed controller can reduce total harmonic distortion (THD) in wide input range by detecting input voltage and adjust the on-time of boost power stage. To achieve high efficiency, the proposed PFC is operated under boundary conduction mode (BCM). The experimental results shows that the proposed PFC can operate at an input line voltage from 90 to 264 Vrms, 400V output voltage and output power from 8 to 80 W. The off-chip inductor and output capacitor are 500 μH and 47 μF, respectively. The maximum efficiency is 95%, the maximum power factor is higher than 0.999 and 8% THD.