Under the comprehensive CIM based modeling, a novel topologic method is presented which divides the distribution network into series of topologic islands according to the types of switches and DGs and their operation states in the networks. According to the structure of design state of the distribution network, the static topologic analysis prepares and stores a lots of sub-trees of topologic islands with their own power supply points in one terminal of bi-directional switches or DG as the main power supply source. Based on the real time states of switches and the role of DG, the dynamic topologic analysis makes the logic reasoning to form a dynamic topologic tree of the distribution networks with the quick assembly of suitable sub-tree of topologic islands which can be directly used for further power flow calculation to meet the real time requirement of on-line mathematic operation. Through the comparison of this algorithm and traditional CIM analysis, this paper verifies the efficiency of the algorithm.