Droop control is one of the common methods of micro-grid inverter control. Firstly, small-signal models of micro-grid inverters are established respectively based on single-loop droop control and dual-loop droop control. Secondly, the impact of droop parameters and load parameters on eigenvalue distribution is studied. This provides theoretical basis for droop parameter design. At last, step responses with the load increased by 20% are obtained from simulation in Matlab/Simulink. The conclusion is that dual-loop droop control has better stability and dynamic response performance than single-loop droop control.