Voltage sag location is basis for voltage sag analysis and control. Based on the optimum allocation of voltage sag monitors, this paper proposes a voltage sag source locating method with multiple screening criteria considering the measurement error. Using the off-line database and collected monitor data, the fault located lines are screened out first, and then the fault located segment on the possible faulty lines is screened with Newton interpolation approach. At last, the fault is located via cost function. The simulation of IEEE 39-bus model verifies the effectiveness and feasibility of the method. Considering the measurement error improves the accuracy of the locating result; progressively screening out the fault location improves the calculation efficiency and weakens the effect of the mistaken fault point.