The 35 kV overhead lines have significantly taller towers compared to the 10 kV lines. However, the lightning protection configuration of the 35 kV lines is relatively insufficient, leading to a higher rate of lightning?induced trip outs. This paper proposes the installation of parallel gaps on a single phase as a means to enhance the lightning withstand level of the lines. Specifically, the parallel gaps are installed on the fixed single phase of the same circuits. The tripping mechanism for the 35 kV overhead lines is inter?phase short?circuit faults. The parallel gaps, when installed on a single phase, utilize the coupling effects to reduce the overvoltages of the other two phases, thereby reducing the rate of inter?phase short?circuit faults and improving the lightning withstand level of the 35 kV overhead lines. By establishing an overvoltage simulation model of 35 kV overhead lines, considering the effects of overhead ground wires and grounding resistance, the impact of parallel gaps on the lightning withstand level of the lines under the single?phase installation mode is calculated. When a single phase is equipped with parallel gaps, the maximum increments in lightning withstand levels under counterattack are 81.9%, 21.2%, and 11.1% respectively, for scenarios with no overhead ground wire, a single overhead ground wire, and double overhead ground wires. Similarly, the maximum increments in lightning withstand levels under induction lightning are 68.2%, 50.2% and 38.4% respectively. Through experiments and calculations, the method to determine the discharge distance of the single?phase installed parallel gaps is proposed according to the probabilities of lightning strikes with different types. Single?phase parallel gaps, characterized by low cost and maintenance?free operation, can serve as important lightning protection measures for 35 kV overhead lines.