Bidirectional DC/DC converters are required in the field of power electronic transformers and DC power distribution networks. In order to apply in different DC distribution grids, the topology of ISOS based on bidirectional DC/DC converters is studied in this paper. The ZVS and ZCS are realized by using LLC resonance in bidirectional energy flow, and resistances are used to realize the voltage-sharing in the topology. Firstly, the experimental waveforms of bidirectional LLC resonant converters are described, then the gain characteristic of the circuit is analyzed by using the fundamental wave analysis method. The same gain characteristic of ISOS topology when the bidirectional energy flow and the realization conditions of soft-switching are the basis of the design of bidirectional LLC converters. The transformers of high frequency and the circuit of voltage-sharing of ISOS topology are analyzed and designed. Finally, two converters of 6.25 kW are developed to verify the analysis method proposed. The DC/DC converters can realize ZVS and ZCS when energy is bi-directionally transmitting, and experimental research confirms the DC/DC converters have the same gain characteristic when energy is bi-directionally transmitting, and the voltage unbalance rate of two converters is less than 3%. This work is supported by Science and Technology Project of State Grid Corporation of China (No. SGRI-DL-71-15-005).