Abstract: DC/DC converter and DC distributed power system have been widely used in many industrial fields, the rule and method to derive the topologies of them were systematically studied in this paper. First, the basic DC/DC converter was functionally divided into three cascaded units which are input unit, conversion unit and output unit, and each unit can further be divided into voltage-type and current-type. Then, according to circuit theory, the topology construction principle was established and four categories of basic DC/DC converters were derived, which were voltage/voltage-type, current/voltage-type, current/current-type and voltage/current-type. The voltage and current conversion relationship of the voltage-type and current-type conversion unit were analyzed in detail. Finally, twelve topologies of the basic DC/DC converter were derived. Moreover, the relationship among input, output and the duty ratio of these converters had been deduced out. Based on the basic topology construction principle above, the basic DC voltage-type and current-type distributed power system were derived. Moreover, simplified DC voltage-type and current-type distributed power system were also obtained. Finally, using high power LED driver as an example, the application of the simplified DC current-type distributed power system had been researched, and the simulation and experiment results were presented in the end.