Abstract: The impedance-based specification is normally used to analyze the stability of multiple inverter system in the state-of-the-arts. However, it is difficult to establish an accuracy output impedance model of droop controlled inverter with the droop control loop, since the control loop is complicated. In this paper, the output impedance of droop controlled inverter was obtained by small-signal method, and parameters of droop control were analyzed based on the derived impedance. It disclosed that the droop control mainly affects the lower-frequency impedance profiles which was determined by Q-U control coefficient. Then, the impacts of dual-loop parameters were also analyzed, it was found that the higher-frequency impedance is sensitivity to voltage closedloop control parameters and capacitance value of LC filter. And a simplified output impedance based on three parameters was built for further verification. Finally, impedance measurement was carried out to verify the validity of the output impedance model, and analyzing method.