There are lots of issues existed with the Power Supply System in DC Building, and it is controversial as these issues have not been solved completely. In recent years, worldwide attention has been focused on proposing the standards of “HVDC power supply system” or “up to 400 Vdc power feed system” following with the development of the power supply system in data center. Many attentions from the worldwide research organizations or institutions have pointed out that these standards can be applied with DC Building. In this paper, the standards of the main organizations and institutions on HVDC power supply system are introduced. Then some definitions of the issues among the standards of these organizations or institutions are analyzed and compared. The requirements for designing the power supply system in DC Building are discussed based on the above issues, including the system topology and the key power electronic converters interfaced to the system. The analysis can be referenced for designing the equipment of the Power Supply System in DC Building and helpful for popularizing the DC Power Supply Technology.