Abstract: Aiming at the difficult problem of user-transformer relationship recognition, this paper implements a user-transformer relationship recognition terminal based on weak characteristic current detection, simulates and analyzes frequency domain characteristics of characteristic current signal, and designs current transformer interface circuit and analog signal conditioning circuit which can work on actual power line. The on-off keying (OOK) demodulation algorithm suitable for characteristic current signal is given. Finally, the prototype is tested. The results show that the characteristic current receiving terminal can correctly receive and record the characteristic current signal sent by the sender on the actual power line, and has achieved good results in the application of user-transformer relationship recognition.