To solve the problem of badly wired and low real-time performance of a low voltage distribution network topology structure, this paper proposes a topology identification method for the distribution network based on the characteristic signal of a smart terminal unit. First, the communication address of the Low-Voltage Intelligent Terminal (LTU) is used to correlate each level switch, and the reactive values at each switch are changed by injecting reactive compensation characteristic signals. Then for the detection results of reactive value in each switch, based on a topology identification strategy, edge computing is performed in the distribution Transformer supervisory Terminal Unit (TTU). The result of the edge computing is the connection relation of switches in the area. The topological structure of low-voltage areas is identified from bottom to top. Finally, the practical engineering value of the topology identification method is proved according by the results from a pilot area. This work is supported by the General Project of National Natural Science Foundation of China (No. 51977059).