The critical conduction mode Boost PFC converter utilizes the resonance to achieve soft-switching, however, leading to high THD and poor power quality, especially at high switching frequency applications. This paper presents a systematic operation analysis of the CRM Boost PFC converter considering the parasitic parameters and investigates the negative influence of resonance process to THD. In order to improve input current THD, a variable on-time control method is proposed to keep the average inductor current following the intended sinusoidal input current. The proposed implementation combines the advantages of digital control and analog control, effectively decreasing the total cost of the system. And the proposed variable on-time compensation method is verified with the experimental results well.