The key load-carrying components of modern high-speed railway vehicles are mostly large-scale welded metallic structures, in which inevitably exist various defects and damages during the manufacturing, operation and maintenance. It is usually argued that, after the safety assessment, those unacceptable quality defects and surface damage are called defects. These defects can considerably decrease the bearing capacity and service life of the structures, it is therefore necessary to repair the bearing parts in the case of defects. This paper summarizes the typical defects existing in the key load-carrying components of railway vehicles and corresponding repair technologies, and then we point out that the structural integrity assessment is the potential research topic and developing direction.