The invention discloses a tool for detecting a steel die positioning pin of a CRTSIII type track slab. The top of a fixed cylinder base is connected with a top cover; a prismosphere mounting groove is arranged in the center of the upper surface of the top cover; a prismosphere is mounted in the prismosphere moutnign groove; a downward-protruded pressure spring positioning sleeve is arranged in the center of the lower surface of the top cover; a gripping rod for fixing the positing pin, an inverse cone body and the pressure spring are arranged inside the fixed cylinder base; a groove is arranged in the center of the inverse cone body; a pressure spring positioning sleeve is arranged in the groove of the inverse cone body; the upper part of the pressure spring is arranged in the pressure spring positioning sleeve; the lower part of the pressure spring is arranged in the groove of the inverse cone body; a slot hole corresponding to the length of the pressure spring positioning sleeve is arranged on the side wall of the fixed cylinder base; a connecting rod of a hand wheel connecting rod passes through the slot hole and is connected with the upper part of the side wall of the inverse cone body; a gripper at the lower end of the gripping rod surrounds the root part of the positioning pin; and the top end of the gripping rod is connected with the conical surface of the outer side wall of the inverse cone body in the mode of sliding contact. The tool can be used for converting the deviation of the steel die positioning pin of the track slab into the deviation of the center of a prism and has the advantages of simple structure, convenience in installation and accuracy in positioning.