Abstract: The cabin door openings are usually arranged in the fuselage for civil aircraft, resulting in fuselage stiffness discontinuity. In view of the structural stiffness and the transmission of the load, the paper studies the opening structure of the fuselage: clarifying the factors affecting the stiffness of the opening structure and optimizing the opening angle and the size of the reinforcing structure. The above research shows the direction and the method of the design and the reinforcement of the opening structure in the preliminary design stage of the opening structure of the aircraft fuselage.