Abstract:A large number of distributed generation ( DG) have a profound impact on the reliability of distribution network.The island operation model is established aiming at the reliability for DG. The traditional minimal cut method is improved combined with the optimal island partition strategy considering the number of customer affected by interruption. The reliability for the four different simulation programs of IEEE RBTS BUS 6 is analyzed,which indicates that DG positions and its capacity will bring different influence on the reliability index. It is also pointed out that the practical operation should take all these factors into consideration so as to lay out the DG to improve the reliability of distribution network.