An underfrequency load shedding（UFLS） strategy is proposed for an islanded microgrid. The characteristics of different distributed energy resources are summed up and a dynamic microgrid simulation model is developed that is composed of the wind turbine-driven doubly-fed induction generator（DFIG）， photovoltaic， fuel cell， microturbine， storage battery and local controller. The frequency control scheme of an islanded microgrid is explored and the relationship between the rate of frequency change， inertia constant and the magnitude of active power deficiency is studied， by means of which the strategy by estimating the magnitude of disturbance to implement UFLS is put forward. Based on the microgrid constructed， the experimental method of obtaining microgrid equivalent inertia is demonstrated. Time domain simulation results show that the proposed UFLS strategy is capable of rapidly and reliably restoring the frequency stability of the microgrid.