So far, the accuracy of the existing methods of fault location based on calculating the impedance at only one terminal of lines is certainly affected by the variation of the system impedance at the remote end. In accordance with parallel lines' special characteristics, this paper presents a method that can calculate the system impedance of the remote end when one of the two lines has fault, so that the effect of its variation can be eliminated completely. This method has been tested by the computer digital simulation, and the results are very satisfactory.