Centering device for track midline ruler

The invention provides a device capable of directly reflecting a track midline position. A centering device for a track midline ruler comprises a crossbeam, a cross shaft is arranged in the middle of the crossbeam, the cross shaft consists of a transverse shaft and a vertical shaft fixed together, the upper part of the vertical shaft passes through a cone, the lower part of the vertical shaft is provided with a prism table, a spherical prism is placed on the prism table, and the center of the spherical prism is positioned on the central axis of the cone. By adopting a simple mechanical device, the midline point of a track is skillfully reflected, and great convenience is brought to field construction and maintenance.