The ideal inverter model and state-less impedance model of network and loads are currently used to analyze the small-signal stability of a microgrid， which will cause important dynamics to be omitted. To capture the dynamics of a microgrid and large power inverters more accurately， a complete small-signal model of a microgrid composed of inverter-interfaced distributed generations is developed. This integrated model consists of two sub-models: one is the small-signal sub-model of network and loads considering dynamics and the other is the small-signal sub-model of inverters including voltage and current controller dynamics. Using the model constructed， the step response results with the active load increased by 20% are obtained， which are verified by the results obtained from simulation of the same situation in PSCAD/EMTDC. The eigenvalues of state matrix of the small-signal model for a microgrid can be used to directly investigate the small-signal stability. A sensitivity analysis is further performed to help identify the origin of the dominant low frequency eigenvalues. The development of the model can optimize the control parameters and improve the small-signal stability of a microgrid.