As one of the structural optimization tools, topology optimization has gained increasing attention due to its powerful design capabilities for generative structures. The conventional topology optimization methods focus on designing single-piece structures, which greatly limits the diversity and breadth of topology optimization design. Therefore, topology optimization has been extended to design multi-component structures, which can be manufactured piece by piece and assembled together. Multi-component topology optimization problems require careful consideration of joints and interfaces between different materials to avoid failure. Current methods assume additional joints like adhesive bonding and welding are needed, but they add complexity and have limitations in accurately describing joint properties such as width and shape. In this research, we propose a new method for designing self-locking mortise and tenon joints in multi-component topology optimization. Mortise and tenon joint is a traditional technique that self-locks two pieces of components without additional joints. Our method generates mortise and tenon-like joints by using interfacial tensile stress constraints to minimize the tensile stress between material interfaces. We also apply dimensional constraints to ensure the integrity of material components. Our proposed method has been verified using numerical examples. By combining interfacial tensile stress and dimensional constraints, we have generated self-locking mortise and tenon joints between different material components. Additionally, maximum stresses between material interfaces have been limited, preventing structural failure caused by excessive tensile stress.