The invention discloses a rail head silhouette measuring instrument, and relates to the technical field of steel rail repair and maintenance. The rail head silhouette measuring instrument comprises a positioning device, a fixing device for fixing a steel rail and a measuring device. The fixing device is arranged at the lower portion of the positioning device. The measuring device is arranged at the upper portion of the positioning device. The measuring device comprises a slide way arranged on a fixed plate, a ruler and a telescopic probe. The ruler slides on the slide way through a slider. The fixed plate can slide up and down and is connected with the positioning device. The transverse probe is arranged at the lower end of the fixed plate and can be meshed with and fixed to the upper end of a rail head silhouette. A standard template is arranged and fixed at the position, corresponding to the probe, of the fixed plate. The grinding amount required by the steel rail and the difference value between the ground steel rail profile and the designed profile can be rapidly measured on working site, the repair and maintenance level of the steel rail is improved, and work efficiency is improved.