With the constantly increasing penetration of distributed generation, some problems such as the low comprehensive operation efficiency of the power system concerned, insufficient coordination among the so-called“source-network-load-storage”, and inadequate complementarity among various types of generators are becoming more and more significant. Implementing hierarchical partition balance of“source - network -load - storage”could address these problems.Under this background, according to the operation rules of a grid- connected microgrid, a diversified power demand block analysis method and a“source-network-load-storage”hierarchical partition balance model are presented, and related optimal design of the distribution network concerned addressed. The proposed method has been employed for actual distribution system planning, and the implementation results demonstrate that this method can effectively reduce the maximum load demand, improve the load profile of the whole system and the load rates of lines, reduce the scale of required network investment, realize coordinated development of“source - network - load- storage”, and finally improve the security and economics of the distribution system.