A modified phase-shift-control method is proposed to solve the problem of narrow Phase-Shift Interval (PSI) and high Disturbance Sensitivity (DS) of inner phase shift to outer phase shift when non-resonant Dual Active Bridge DC-DC converter (DAB) in solid state transformer with dual-phase-shift control transmits light-load power. Firstly, by comparing and analyzing the operation principle and power transmission characteristics of DAB under the traditional Phase-Shift-Control (PSC), the intrinsic relationship among the PSCs is established. Secondly, according to the operation principle of the modified dual phase shift control method, three operation states are classified and the modes of each operation state are studied. Then, the transmission power of each operation state is deduced and its transmission characteristics are analyzed. The theoretical analysis shows that compared with the traditional PSC method, this method can significantly reduce the DS of inner phase shift to the outer phase shift and the impact on transmission power, broaden the PSI of inner and outer phase shift and improve the power transmission efficiency of the system. Finally, the correctness and superiority of the proposed method are verified by simulation. This work is supported by National Natural Science Foundation of China (No. 51777120) and Shanghai Engineering Research Center of Green Energy Grid-connected Technology (No. 13DZ2251900).