The size of the cantilever beam embedded parts pressure plate should not be less than 100mmX10mm (width x thickness). The cantilever beam is a statically determined structure, and the reliability of its connection is the key to the extension and reconstruction of the cantilever beam, while the joint surface between old and new concrete is the weak link in the reconstruction and reinforcement. By analyzing the factors that affect the bonding performance of old and new concrete, multiple measures were taken to ensure the reliability of the cantilever beam extension.