Abstract: H-shaped steel bolted welded joints have excellent welding performance and are widely used in steel buildings. However, during the construction, the joints often show welding defects such as misalignment, air holes, and slag inclusion, which do not meet the requirements of acceptance specifications and seriously affect structural safety. In order to ensure the safe use of structures, it is necessary to study the method for accurately evaluating the bearing capacity and the reinforcement technology in a confined space of the defective H-shaped steel bolted welded joints. In this paper, defective welds were quantitatively classified into different levels, and a method for accurately evaluating the residual bearing capacity of joints by using the effective part of the defective welds, bolt friction, and compressive capacity of the defective welds was proposed. In addition, joints of five commonly used beams with different defective welds were evaluated, and the evaluation results of the bearing capacity of each joint were given. According to the evaluation results, a bending reinforcement method of H-shaped bolted welded joints was proposed, which changed H-shaped structures into III-shaped sections in a confined space. The research results can provide a reference for the identification and reinforcement of defective H-shaped steel bolted welded, as well as the revision of reinforcement codes of steel structure joints in China.