The fireproof expansion sealing strip is used between the door leaf and the door frame, the door leaf and the door leaf of the steel door and the wooden door. When a fire breaks out, the fireproof expansion sealing strip voluntarily expands, seals the gap between the door, and isolates the air circulation between the two spaces, effectively avoiding the damage to the human body by the thick smoke, toxic gas and hot air in the early stage of the fire and controlling the extension of the fire. The sealing strip can be glued in the groove of the fire door seam, or can be fixed in the groove of the fire door with a small nail. Features: 1. Expansion temperature; 2. Linear expansion multiple; 3. High temperature resistance and incineration function; 4. Smoke prevention function; 5. Environmental resistance.