In order to reduce the influence of monitoring blind area caused by the uncertainty of fault resistance on voltage sag source location in transmission line short-circuit fault, a voltage sag source location estimation method based on optimal configuration of system monitoring points and fault parameter estimation is proposed. Considering the observability of voltage sag in various short-circuit faults, the importance index of measuring points in the system is proposed, so as to construct the optimal configuration model of monitoring points. Based on the optimal configuration scheme of monitoring points, the sag source location model is established, and the adaptive cuckoo algorithm is used to estimate the parameters of fault line, fault resistance and fault distance. Finally, the simulation is verified by IEEE-30 node standard test system. The results show that the proposed method has higher fault location accuracy and more engineering applicability than the traditional method.