In this paper, a digital variable on-time control (VOT) and primary side regulation (PSR) applied to a power factor correction (PFC) flyback converter is realized. This PFC flyback converter is operated in the critical conduction mode (CRM). Compared with constant on-time control (COT), VOT control can decrease total harmonic distortion (THD) of input current and make high power factor (PF). The method which is used to obtain output voltage is PSR. This method can sense output voltage by auxiliary wind without opto-coupler. This PFC flyback converter worked in universal input voltage 90∼264Vac and the output power is 36W with output DC voltage 36V. The proposed control method is implemented by field-programmable gate array (FPGA). Experimental result are shown that PF is higher than 0.95 and THD is less than 10%.