The evolution rule of modal parameters of rail vehicle system is closely related to the vibration response characteristics, and thus affects the vehicle running quality. Frequency veering is a typical phenomenon in the evolution of system modal parameters. Based on fuzzy clustering and vehicle system dynamics model, the frequency veering research in the process of vehicle system modal evolution under speed change is carried out, and the relationship between vehicle system frequency veering and vehicle response characteristics is further explored. The results show that the combination of dynamic model and fuzzy clustering method can clearly track the evolution of vehicle system modal frequency and damping ratio; With the increase of running speed, the frequency veering occurs between the hunting modal frequency of bogies and the modal frequency of rigid car body, and the modal damping ratio changes significantly; The vibration response corresponding to the two modes with frequency veering is significantly increased. Moreover, at the speeds corresponding to the frequency veering, the vibration amplitude of the car body increases, and the vehicle running quality deteriorates significantly.