Abstract: Inverter interfaced distributed generator（IIDG） is a nonlinear complex system with multiple time scales including frequency control, time delay measurement and electromagnetic transient. The droop control based IIDG of microgrid was taken as research object and its detailed model consist of power droop controller, voltage-loop and current-loop controllers, filter and line were established. Based on the singular perturbation theory, the multi-time scale characteristics of the IIDG detailed model were divided, and the model order was reduced by neglecting fast dynamics. The static and transient stability consistency of IIDG original and reduced systems were demonstrated by feature extraction of IIDG small signal model and the quadratic approximation method of the stability region boundary respectively. Time-domain simulation results demonstrate the proposed model reduction method and multi-time scale division method are effective and applicable to provide simplified model for dynamic characteristic analysis of the IIDG system in microgrid.