Ensuring the integrity of high-speed (HS) trains is essential for their large-scale and long-term safe operation. This paper presents a generic framework for defining and assessing the integrity of HS train systems in which vehicle system dynamics play a central role. First, the concepts of structural integrity, dynamical integrity, and system integrity of HS trains are defined. The system integrity relies on the structural integrity of train components and the dynamical integrity of the whole vehicle system. The dynamical integrity directly affects the dynamical performance of HS trains as well as the degradation and failure of train components. Then, the general strategies for assessing the structural integrity of HS trains and the general principles for assessing the dynamical integrity of HS trains are discussed. Further, numerical, experimental, and operational approaches for assessing the dynamical integrity of HS trains are introduced, including coupled dynamics theory, tailored test benches, and monitoring and prognostic methods. These theories and practices effectively support the integrity assessment and safe operation of HS trains in China.