In order to improve the efficiency of Dual Active Bridge (DAB) converters and simplify the complex time-domain analysis process of DAB converters, the article proposes a modulation strategy with minimum current root mean square (RMS) using vector analysis method. The analytical expression of the DAB converter was derived, and the modulation strategy with the current RMS as the optimization objective was intuitively derived using vector analysis by extracting the fundamental component. Compared with the modulation strategy under the traditional time-domain analysis, it does not need to solve the equation of state of each period in the switching cycle, which greatly simplifies the analysis process of the DAB converter. Especially in light load situations, this strategy can effectively reduce the inductance current and improve the transmission efficiency of the converter. Finally, an experimental platform was built to verify the effectiveness of the optimized modulation strategy proposed in this paper.