A novel topology of isolated input-series and output-series (ISOS) full-bridge bidirectional DC/DC converter is described in this paper for the application requirement of high input voltage and high output voltage, which can be used in the next generation medium and high voltage power conversion systems. The proposed novel isolated bidirectional DC/DC converter not only can apparently decrease the stress of the switches, but also have the advantages, such as galvanic isolation, ease of realizing soft-switching control, high power density, and so on. In this paper, working principle of the proposed DC/DC converter is discussed in detail, the corresponding equations are derived, and the soft switching implementation is discussed too. In the end, simulation is done through PSIM to certify the feasibility of the proposed DC/DC converter and accuracy of the criterion.