Abstract: The operation of bidirectional DC-DC converter in Buck mode is one of the factors leading to resonant instability of DC distribution system because of negative damping performance. Aiming at the resonant instability of DC distribution system composed of VSC and bidirectional DC-DC converter, we construct an analytical model by using the state space modeling method. The influences of steady-state operation points, main circuit parameters and control system parameters on the characteristics of DC distribution system are studied to reveal the mechanism of resonant instability. To suppress the instability, a damping control strategy of feedback DC current into the current inner loop of VSC is proposed. This damping control method can be employed to suppress resonant instability by adjusting the instantaneous power injected into DC distribution system in real time. And then, the range of damping controller parameters is analytically calculated under the two constraints that there is no impedance magnitudes intersection in low frequency range and the phase difference of two impedances of the impedance magnitude in the medium frequency range is within 180°. The main factors influencing the selecting range of parameters are also studied. Finally, in the ranges of the calculated parameters, four points of rectangular box are selected for electromagnetic transient simulation verification, the results of which present the correctness and effectiveness of the proposed method.