Disclosed in the present invention are a combustion furnace with coaxial staged hearth and heating method thereof, in which the combustion furnace comprises a metal furnace body (40) whose internal part is provided with a furnace chamber. The furnace chamber is divided into two sections at the middle by fire resistant material to form a left and a right independent combustion chambers (18, 19). Two independent combustion chambers (18, 19) are respectively connected with the ends of flue gas chambers (2, 60), while the other ends of the flue gas chambers (2, 60) are respectively connected with a burner (3). The peripherals of two independent combustion chambers (18, 19) are respectively provided with a flue gas heat radiation pipe (14). A middle flue gas chamber (100) is set in the middle position of the furnace chamber. Two ends of the flue gas heat radiation pipe (14) are respectively connected with the flue gas chamber (2, 60) and the middle flue gas chamber (100). Two independent combustion chambers (18, 19) are communicated with each other through the flue gas chamber (2, 60), the flue gas heat radiation pipe (14) and the middle flue gas chamber (100), and combust alternately. A suspension device including a portal frame (50) is provided for suspending the metal furnace body (40) horizontally or obliquely. The metal furnace body (40) is suspended on the portal frame (50) at a suspending point (41). A walking mechanism (20) and a feeding mechanism (9) are also set on the portal frame (50).