To reduce the current stress of a dual-active-bridge (DAB) DC-DC converter and improve its efficiency, an optimal control strategy for current stress segmentation of the DAB converter under double phase shift control is proposed. The strategy first analyses the structure of the DAB converter and its power characteristics, and derives the relationship between current stress and transmission power and phase shift angle. Then, the current stress of the DAB converter is optimized in segments for the case of mismatched input and output voltages, and the optimal phase shift angle of the DAB converter is obtained for different transmission power ranges by segmenting the transmission power. The proposed control strategy is analyzed and compared with conventional double phase shift control strategy, and it is found that the proposed control strategy has smaller current stress and return power. This reduces the conduction loss of the converter and improves the efficiency of the converter. The dynamic performance of the DAB converter is greatly improved when the load changes abruptly. Finally, an experimental prototype is built based on the proposed control strategy, and the experimental results verify the correctness and effectiveness of the proposed control strategy.