Aiming at the problem that the two-phase interleaved buck system is disturbed, the output fluctuates greatly and the recovery time is longer. Based on the differential flat theory, a flat control strategy is proposed. A differential flat controller is designed. The controller is divided into two parts: feedforward controller and feedback compensator. The feedforward controller can cancel the nonlinear characteristics of the system and make the system follow the desired output trajectory. The feedback compensator is used to eliminate the cause. The phenomenon that the system output deviates from the desired trajectory caused by interference and unmodeled parts of the system. When the differential flat controller output voltage is changed, it can re-follow the expected output of the system in a shorter time, and has better anti-interference ability when the interference occurs. The controller has certain reference value in improving the dynamic characteristics of the system.