Abstract: Isolated bidirectional dual-active-bridge dc-dc converters（IBDC） with single-phase-shifting（SPS） control strategy would produce large backflow power and current stress which lead to increasing losses. This paper proposed a backflow-power-optimized dual-phase-shifting（DPS） control strategy by establishing the mathematical models of transmission power and backflow power of the IBDC, deducing the relationship equation between the backflow power and phase-shift ratios and the input/output voltage conversion ratio. This strategy is aiming to minimize the backflow power. The optimal phase-shift ratios were calculated by using the segmentation optimization algorithm in different ranges of transmission power and input/output voltage conversion ratio. The backflow power curves under the proposed DPS and SPS control conditions were analyzed and compared. Then an optimization control algorithm and a system control scheme of the IBDC were presented, furthermore an experimental prototype was developed based on this strategy. The experimental results verify the effectiveness and feasibility of the proposed control strategy.