With the increasing permeability of distributed generation (DG), the self-healing function of smart distribution network will be a key to the construction of smart grid, and island partition will be a core technology of self-healing in distribution network. This paper firstly introduces the graph model of distribution network integrated with DGs, and builds the mathematical model of islanding problem. Then, based on the main principles of island division of distribution network, the method of selecting power supply path for load recovery is analyzed, and the concept of islanding circle and power supply recovery coefficient is innovatively proposed. On this basis, a new set of heuristic rules for island partition is summarized, and a new method for searching island called "circle-shrink method" is proposed. Finally, the simulation result shows that this method can solve island partitioning problem of distribution network integrated with DGs more quickly and effectively