Overvoltage is easily caused when an electric locomotive goes through an electrical sectioning device, thereby leading to the breakdown of the equipment’s insulation. A bilateral passive RC suppression method is proposed to restrain overvoltage using an eight-span overlapping electrical sectioning device. The maximum overvoltage on the bilateral passive RC circuit of the eight-span electrical sectioning device over 60 kV and suppressive effect is obvious. Operating experience and experiments show that overvoltage is caused by electric locomotive going through seven-span electrical sectioning device in a short time. However, when electric locomotive goes through double-neural section electrical sectioning overlap, threefold overvoltage still may be produced, which is close to the value of overvoltage of locomotive roof insulation. Former researches pointed out that low-frequency oscillation voltage of neutral line has a great effect on overvoltage. Thus, in order to study overvoltage protection, bilateral suppression circuit is adopted in the double-neutral section.