The invention discloses a method for removing thick-layer limescale at the bottom of a boiler, and belongs to the field of limescale removing. According to the method, a prepared viscous solution is cured on a needle, the needle is inserted into the limescale, soft water is added, and heating is conducted, so that a solid on the needle is melted and makes contact with an interface, and then the limescale is disengaged; a scale inhibitor is prepared, and the boiler bottom subjected to limescale removing is smeared with the scale inhibitor to be protected. According to the method for removing the thick-layer limescale at the bottom of the boiler, a chemical method is combined with a physical method, a good descaling effect on the limescale with large thickness is achieved, the descaling time is short, the good scale inhibition performance is achieved due to the fact that the prepared scale inhibitor is used for protection, biodegradability is achieved, and toxicity does not exist.