The invention discloses a power distribution network island dividing method considering internal and external equivalent electrical distance of a power supply group. The power distribution network island dividing method considering internal and external equivalent electrical distance of a power supply group can realize minimization of internal interconnected impedance in the power supply group to effectively improve the overall power supply capability of the whole power supply group by considering the internal interconnected impedance level in the distributed power supply group and by means of changes of the on/off state of the interconnection switch in the power distribution network during the island dividing process. Besides, during the load fusion process, the power distribution network island dividing method considering internal and external equivalent electrical distance of a power supply group firstly calculates the equivalent electrical distance between single load and the whole power supply group, and secondly performs power supply fusion according to the sequence from small equivalent electrical distance to large equivalent electrical distance, overcomes the limitation of only considering the electrical distance between single power supply and single load, and considers the characteristic that the practical power of a plurality of power supplies for load power supply is flowing in the island range so as to reduce the line loss in the island on the whole and realize the power supply range satisfying the maximum load requirement.