For the dual active full bridge converter system, the dynamic response speed is slow when the system is disturbed. Based on differential flatness theory and single-phase-shift control, this paper presents a flat control strategy. In this paper, the flat control system of DAB converter is designed, including two parts of feedforward control nonlinear error feedback control: feedforward control uses the desired output to plan the state variable trajectory; nonlinear error feedback corrects flat output and eliminates errors. This paper proves the stability of the flat control. Finally, the DAB converter flat control and PI control are simulated on the simulation platform. The results show that: when the DAB converter output voltage setpoint changes, the input voltage fluctuates and the load changes, Under the flat control strategy, the DAB system can achieve faster output stability and the system has better dynamic performance.