In order to improve the accuracy and rapidity of voltage sag location and traceability in China's domestic distribution network，a propagation model and analysis method of the voltage sag amplitude under the same voltage level is proposed．Firstly，a horizontal propagation model of the voltage sag amplitude of the distribution network is established．Taking the size of the fault resistance and the electrical distance from the fault point to the monitoring point as the key fault parameters，the fault resistance and fault distance characterization forms of the voltage and line current at each monitoring point are proposed．Secondly，the propagation characteristics of voltage and the current with the fault resistance and fault distance are analyzed; Finally，the simulation verified the validity of the voltage sag propagation model and the correctness of the propagation characteristics．

voltage sag , horizontal propagation , fault resistance , fault distance