Abstract: The paper introduces the development of high speed railways in the world and the detailed plans of high speed railway development in China in the near future. A few serious derailment accidents of high speed trains in the world are listed and the corresponding causes are briefly described. The paper emphasizes a few key scientific problems in theoretical evaluation for high speed train safety operation, which arise from the theoretical modeling and the corresponding numerical performance for such a large-scaled system under high speed operation and abnormality. The abnormality indicates the failure of some key components in the trains or the tracks, or the trains passing through strong cross-wind and cyclone, and earthquake occurring when the trains running. The advantages and disadvantages are discussed of the existing theoretical models and their numerical methods for railway vehicles coupled with tracks. These models need to be further improved to be suitable for the evaluation of the dynamic behavior and safety operation of high speed trains running in the abnormal situations. The improvement of the models includes the spatial modeling extension of the coupled structures and the analyzed frequency range, replacing the linear models by the nonlinear models for the key links between the components, such as suspension systems of the vehicles, the fastening systems of the tracks, etc., introducing failure models for some parts, and boundary modeling for cross-winds, tornados and earthquakes. The study on the running safety of high speed trains in operation is indicated.