The fluctuation of intermittent distributed generator and load complicates the evaluation of island operation reliability of microgrid. The temporal correlation between load states is strengthened by the adoption of a practical short-term load shedding strategy

which avoids frequently shedding and recovering load in the islanded mode. Based on this strategy

the computation burden of squential Monte Carlo simulation is heavy. Based on geometric distribution and probability calculation

this paper proposes a group of analytic formulas to quickly and accurately calculate the probability distribution of power outage time at microgrid load points. Then the load points and microgrid reliability indices can be calculated. Taking the reconstructed power distribution system as an example

the proposed method is compared with the Monte Carlo evaluation method by evaluating the island operation reliability in the microgrid

which verifies the rapidity and effectiveness of the proposed method. The effect of source-load fluctuation and load shedding strategy on the islanded operation reliability in the microgrid is analyzed

which further validates the rationality of the proposed model.