Traditional current balance protection on double-circuit transmission line can not react to the interline fault, thus a current balance protection based on the same directional component current phase selection is proposed. First, the fault phase selection is realized by using the incremental quantity of the same directional component current. The discriminant method of two-phase short circuit and three-phase short circuit is provided. Then, the ratio of the opposite direction component current to same directional component current is used to judge whether the fault phase is interline fault. For the interline fault phase, the fault location is determined by distance protection of singe-circuit transmission line. For singe-circuit transmission line fault phase, the fault line selection is determined by the magnitude of the same-name-phase. The six-sequence fault component is used to analyze the phase selection criterion and the protection criterion under different fault types, and a specific protection process is proposed. The correctness and effectiveness of the proposed scheme are verified by both theoretical analysis and ATP-EMTP simulation results. The scheme can react to the interline fault and the protection performance is improved. This work is supported by Natural Science Basic Research Plan of Shaanxi Province of China (No. 2014JM7293) and Science and Technology Project of the Headquarter of State Grid Corporation of China (No. SGTYHT/16-JS-198).