According to insufficient sensitivity of distinguishing permanent faults from transient faults in some cases, a distinguishing method of single-phase adaptive reclosure for the asymmetrical three-phase transmission lines is proposed. The equivalent circuit of the asymmetrical three-phase transmission lines is established, and the calculation formula of recovery voltage of fault phase is derived, and the factors of influencing recovery voltage amplitude are analyzed under permanent faults or transient faults. The results show that the recovery voltage amplitude is affected by transient faults or permanent faults, the direction and size of the power flow, the fault phase and the fault location. So the new method which uses corresponding threshold in different conditions is proposed. The EMTP simulation results verify the correctness and effectiveness of the proposed method and it can improve the success rate of reclosing. This work is supported by Natural Science Basic Research Plan of Shaanxi Province (No. 2014JM7293) and Natural Science Research Plan of Education Department of Shanxi Province (No. 15JK1513).