Abstract: Distribution transformers serve as an important entity for electricity supply and demand, as well as the intersection where the distribution systems fault and power quality issues can adversely affect generation, network, load, and storage. However, the classical transformers have drawbacks, such as uncontrollability, inability to isolate faults, and lack of fault ride-through capability. Achieving flexible control and optimized distribution network operation with these limitations is challenging. Recently, some scholars have extensively researched flexible and controllable hybrid distribution transformer (HDT) technologies by proposing various topologies and control methods. However, these research efforts have not been systematically summarized and analyzed. Therefore, we first analyze the application demands of HDTs for new-type distribution systems. Then, we review the development history of existing HDTs and summarize the key technologies involved in HDTs. Specifically, these technologies include the topology of HDTs integrating power-frequency transformers and converters in series and parallel connection, coordination techniques for control strategies, protection at the converter and device levels, integration design and its key components, and standardization of HDT technologies. Finally, we discuss the key constraint factors and future directions for HDT development. The proposed review provides new insights for developing and researching intelligent distribution transformers for new-type distribution systems.