Abstract: Accurately identifying the topology structure of the low-voltage distribution transformer area plays an important role in understanding the operation status, equipment information, and electricity consumption information of the electricity customer end equipment. The topology identification method of low-voltage distribution transformer area based on power line carrier communication can save resources and accurately collect user side information. This paper proposes a strategy for adaptively dynamically adjusting the number of available subcarriers in OFDM based on power line communication to identify the topology of the distribution transformer area. Firstly, the channel state is estimated, and for reliable communication nodes, power is allocated to each subcarrier according to the estimation results; For unreliable nodes, the subcarrier channel state is estimated sequentially through polling, and all available subcarriers are selected and power allocation algorithms are used for power allocation, attempting to communicate with the station terminal. If the communication is successful, the system will enter a normal communication state. If communication is unsuccessful, gradually reduce the number of subcarriers and close the subcarrier with the worst channel state until a feasible communication solution is found. The effectiveness of the proposed method is verified based on the OPNET platform, which ensures the accuracy of topology identification while improving the overall transmission performance of the system.