In view of the effects of operating loss on a dual-active-bridge(DAB) DC-DC converter, the characteristics of output power from the DAB converter were analyzed considering the switching device loss. First, according to different operating modes of the DAB converter and the operating characteristics of switching devices, a model of switching device loss under the dual-phase-shift modulation strategy was established, based on which the distribution of output power considering the switching device loss was derived. In addition, the characteristics of the output power were analyzed. Compared with the ideal output power, the maximum output power point considering the device loss was shifted to a direction along which the loss was smaller, with the offset trend related to the parameters of switching devices. Finally, an experimental platform was built to conduct the verification, and experimental results verified the offset trend accuracy of the maximum output power point.