Abstract: This paper focused on a DC microgrid with droop control structure. The small-signal models had been derived in the s plane. Eigenvalue analysis results revealed the relationship between system stability and the parameters of DC system, such as DC load power, the type of DC load and the droop gains. It shows that when the converter adopts the detailed modeling, the poorly damped LC filter in DC microgrid, which consists of the capacitor of converter and equivalent reactance of connecting cable, will have interaction with the output impedance of converter and may reduce the system damping and bring in unstable high-frequency oscillations. Based on the impedance ratio type criterions, a low-pass-based active damping method was proposed to change the original unstable root locus and overcome the unstable oscillations by reshaping the equivalent output impedance of DC-DC converters. Simulation and experimental results were carried out to confirm the validity of the proposed approach.