The invention discloses a safe automatic steel-loading positioning device and a method for a heating furnace. The device comprises a laser range finder, a furnace-in roller way and a charging cantilever roller way. The method comprises the following steps: installing the laser range finder; feeding steel through the furnace-in roller way to the heating furnace at a speed of 1.2-1.5m/s and meanwhile enabling the a charging cantilever roller way in the furnace to run at a speed of 1.2-1.5m/s; starting the laser range finder to carry out positioning operation when the laser range finder senses that the head of a billet head passes through 2/3 of the length of the billet; determining the delayed time when most of the billet passes through the laser range finder according to the positioning distance and speed when the head of the billet head passes through 2/3 of the length of the billet, and judging whether almost billet passes through the laser range finder or not so as to reduce the speed of the furnace-in roller way and the charging cantilever roller way to 0.4m/s; and stopping the roller ways within a period of time delayed after the laser range finder senses that the tail of the billet departs, and finishing positioning. The device disclosed by the invention solves the problem that existing strokehold cold and hot metal detector which can be spuriously triggered by black smoke, mobile objects and the like easily cannot judge whether failures exist or not and cannot reliably ensure that the billet completely enters the furnace, and meanwhile, the positioning speedability and the safe reliability are improved.