Multi-circuit transmission lines on the same tower have become the inevitable trend of power grid construction, mostly partial coupling mode. Affected by the partial coupling characteristics, the existing fault location methods have large error. Therefore, this paper develops a study about the fault analysis and fault location method for the partial decoupling double-circuit transmission lines. Based on its structure and characteristics, as well as the lines decoupling theory, the interface equations of demarcation point are built. On the basis of the above study, the new fault location algorithm based on time-domain for partial coupling double-circuit transmission lines are presented. Finally, ATP/EMTP is used to construct the model of partial coupling of double-circuit transmission lines. After the overall simulation and verification, it shows that the presented algorithm is accurate. This work is supported by National Natural Science Foundation of China (No. 51307065).