The OVPD device is an important component of the protective equipment in the power supply system of urban rail transit. Basic principle of rail potential limiting protection for urban rail transit was analyzed, and a new type of rail potential limiter for urban rail transit was designed, which provided the basis for the selection of the thyristor of the rail potential limiter through the calculation of short-circuit current, and determined the appropriate thyristor parameters. Meanwhile, a voltage controlled circuit based on high-voltage trigger diode was designed which was used to adjust the operation voltage of the rail potential limiter. The test results showed that the new type rail potential limiter was reliable and stable, which could meet the requirement of performance. It was also suitable for flexible setting of different metro lines.