Based on the typical manner of electric locomotive passing the neutral section, equivalent circuit model was established of the three kinds of voltage transformer according to electromagnetic induction, the resistance partial pressure and capacitance partial pressure. Transient process of electric locomotive passing the neutral section was simulated, especially the mechanism of overvoltage. The results showed that electronic voltage transformer based on capacitance partial pressure could eliminate resonant overvoltage, and reduce the operating overvoltage effectively. It is beneficial to improve transient process of electric locomotive passing the neutral section and reduce the traction network insulation accidents.