The stability analysis of traditional power grid is based on generator;however，for the microgrid the stability analysis is based on converters.The difference requires that a new model for microgrid stability analysis should be constructed.The paper divides the converters into two types，i.e.voltage source and current source.The small-signal model of a microgrid is obtained through state space method.The autonomous system model of this microgrid is obtained by nodal power calculation，and the stability analysis is carried out based on this model.A time domain simulation model is constructed in MATLAB，and the stability analysis is validated by the simulation results.