In this paper, an improved method to extend the zero-voltage-switching (ZVS) input voltage range and leave a time margin for the totem-pole power factor correction (PFC) rectifier is proposed. With the new method, the calculation of variable on-time control critical conduction mode (CRM) is greatly reduced. The efficiency of traditional ZVS software algorithm in a line cycle operation is increased. The method is validated by a 600 W GaN-based totem-pole PFC rectifier simulation model. Simulation results verified the rationality and effectiveness of the improved ZVS time calculation algorithm.