Switching-mode AC/DC converters are widely used in modern power supplies for computers, data centers and tele-communication equipment. Achieving Power Factor Correction (PFC) and high efficiency are the two most important require-ments. In many cases, high power density is also of tremendous interest. Both power efficiency and power density are greatly influenced by the power devices, the topology and the control used. Compared with conventional Si power MOSFET and Si su-per-junction MOSFET, the newly introduced 600 V GaN devices not only eliminate the reverser recovery, but also have much lower switching and driving losses. These excellent properties enable the emergence of the totem-pole bridgeless AC/DC converter as the next generation preferred solution for PFC instead of the state-of-the art Si-based boost PFC. In this paper, the key technologies and designs for both hard-switching and soft-switching GaN totem-pole PFC are reviewed and the key performance metrics are compared. A soft switching, 3.2 kW totem-pole PFC prototype with 99% efficiency and 130 W/inch3 power density has been achieved in the author’s group as a proof of the concept. Based on the power density comparison, the high frequency soft-switching GaN totem-pole PFC is the preferred choice to achieve both high efficiency and high power density at the same time.