Random outputs of photovoltaic generators and wind power generators take a great proportion in islandedmicrogrids,and the loads are random.However,certain power flow only reflects the operation state at a certain mo-ment.In order to reflect the real power flow distribution in islanded microgrids more correctly,probability models ofphotovoltaic generators and wind power generators in microgrids are constructed,and the power flow of a real islan-ded microgrid system is analyzed by using a calculation method based on the semi- invariant and the Gram- Charlierseries expansion,which verifies the effectiveness of the proposed method.From the results of stochastic power flowanalysis for the diesel generator on or off operation,it is found that the addition of storage devices helps reduce thevariation of voltage and guarantee the reliability of microgrids.