Abstract: To address malfunction and refusal of traditional current protection caused by complex fault currents after flexible loop operation in an old urban distribution network, this paper proposes a three-layer adaptive current protection system of state awareness-adaptive setting-fast fault response. Based on field data and fault simulation, the method achieves adaptive loop recognition, precise fault current perception, dynamic setting adjustment, and coordinated fast-selective protection. It ensures reliable fault isolation and improves power supply reliability and safety of looped distribution networks.