The invention provides an automatic armor steel positioning device for a heating furnace. The automatic armor steel positioning device comprises a furnace inside positioning machinery connecting rod, a limiting switch, a baffle and a baffle position retaining device, wherein the furnace inside positioning machinery connecting rod comprises a furnace inside part and a furnace outside part; the furnace outside part is used for mounting a limiting switch shifter; the baffle is arranged on the furnace inside part and positioned in a path by which a steel billet enters the heating furnace; when the steel billet is contacted with the baffle, the baffle is used for driving the furnace inside part, the furnace inside part is used for driving the furnace outside part and the limiting switch shifter; the limiting switch shifter is connected with the limiting switch and used for driving the limiting switch; the baffle position retaining device is connected with the furnace outside part and used for keeping the baffle in an initial position when an external force is not applied to the baffle. The automatic armor steel positioning device can be used for accurately and effectively positioning the steel billet, effectively determining the position of the steel billet, preventing the steel billet from colliding with the furnace wall of a furnace opening of the heating furnace and impacting the buffer baffle, and effectively improving the production safety and reliability.