Abstract: With the large-scale collection of new energy sources and the continuous expansion of the power grid, the HVDC transmission capacity continues to increase. Interconnecting DC systems of different voltage levels will become an inevitable trend of DC power grids in the future. DC/DC converters play a key role in the interconnection of multiple voltage levels. Firstly, we summarized the characteristics of the existing DC/DC converters with high-voltage and large-capacity and presented the classification and comparison of different aspects. Based on the above-mentioned work, we discussed the suitable DC/DC converters for different types of power sources and different grounding methods, and proposed the suitable topology type. Finally, the demand analysis of the DC/DC converters used in the multi-voltage level interconnection was carried out from the two aspects of power flow control and different operation modes. The content of this paper can provide a certain technical reference for the theoretical research and engineering application of DC/DC converters for multi-voltage DC interconnection.