Abstract: Aiming at the problem that the dual active bridge (DAB) converter cannot truly achieve the global optimal inductor current stress under one phase shifting strategy, a full phase-shifting modulation optimization algorithm based on a matrix transformer is proposed. Through comprehensive analysis of the effects of six phase-shifting modes composed of three phase-shifting degrees of freedom on inductor current stress, and the combine of the mathematical model of transmission power, the global optimal solution corresponding to all voltage transmission ratios can be obtained. A new type of matrix transformer structure with low-voltage side in parallel and high-voltage side in series is used. The influence of the fourth phase shift angle introduced by the structure on the optimization results is analyzed. Finally a modulation optimization algorithm is applied to this topology via direct power control. The simulation and experimental results show that the modulation optimization algorithm proposed in this paper can optimize the global inductor current stress of the DAB converter, improve the working efficiency, and realize soft switching at light loads.