Fire doors are installed to prevent the spread of fire in a building, whereby gaps between the door frame and door leaf are blocked using gaskets of various materials and shapes. However, there are many difficulties in ensuring the desired performance. This study focuses on the research and development of a double gasket that can improve the fire resistance performance of a no threshold fire door, in which the door frame under the fire door has been removed. This is a product that has been researched and developed to improve fire resistance and airtightness in no threshold fire doors by connecting it to the gasket to ensure there is no breakage.