The invention discloses a fire well mouth repairing method for an anode carbon roasting furnace. The fire well mouth repairing method is characterized by comprising the following steps that (1), a round groove is machined in the upper end of a broken fire well mouth; and (2), an annular repairing block with the inner diameter being the same with the inner diameter of the broken fire well mouth is made. Meanwhile, the invention further discloses a repairing tool for repairing the fire well mouth of the anode carbon roasting furnace. The repairing tool is characterized by being composed of a mounting base (1), a sliding rail (2) arranged on the mounting base (2), a sliding block (3) arranged on the sliding rail (2) and capable of moving up and down along the sliding rail (2) and the like. The round groove is formed in the broken fire well mouth, and the annular repairing block is mounted in the round groove, so that the broken fire well mouth is repaired, and the repaired fire well mouth is the same with an unbroken fire well mouth in size. Compared with a traditional method adopting fire-resistant cement gum to repair, the service life of the repaired fire well mouth is longer.