Dual Active Bridge (DAB) DC-DC converters have been widely used in energy storage, distributed energy, and electric vehicles due to its electrical isolation, high power density, and easy implementation of soft switching. However, under extreme operating conditions, DAB converters suffer from high current stress. Regarding the demand of wide voltage-gain range, variable transformer turn ratio can be adopted based on dual-phase-shifting to maintain high efficiency. In this article, a set of turn ratios is obtained that minimizes the average current stress of the inductor within a given transmission power and input/output voltage range using the proposed dual-phase-shifting optimization algorithm. The turn ratio is switched within the range of output voltage variation that optimizes the current stress. A mathematical relationship between the output voltage and phase-shift duty cycle of all operating modes under dual-phase-shift control is established, which can realize the lowest average current stress in the full operating range of the converter by separate optimization of two phase-shift duty cycles on both sides. Simulation in MATLAB/Simulink verified the correctness of the proposed strategy.