Abstract: If a failure happens as the distributed generation operates under the isolated island, the output current of microgrid is limited, so the traditional over current protection is no longer suitable for microgrid. The author selects radiant microgrid to study, and then focuses on the simulation of fault characteristics of microgrid paralleled in distribution network and in the island state by simulation model build by PSCAD/EMTDC software. Adopt the microgrid protection scheme which combines over current protection with negative sequence current protection based on the fault characteristics of microgrid. The analysis result shows that the protection scheme can satisfy the protect requirements of microgrid.