A new fault location algorithm for double-circuit transmission lines is described in this paper. The proposed method uses data extracted from two ends of the transmission lines and thus eliminates the effects of the source impedance and the fault resistance. The distributed parameter model and the modal transformation are also employed. Depending on modal transformation, the coupled equations of the lines are converted into decoupled ones. In this way, the mutual coupling effects between adjacent circuits of the lines are eliminated and therefore an accurate fault location can be achieved. The proposed method is tested via digital simulation using EMTP in conjunction with MATLAB. The test results corroborate the high accuracy of the proposed method.