In order to solve the vehicle transverse swing problem in the railway turnout, this paper discussed the influence of curved switch rail on vehicle transverse swing through field testing and numerical simulation. A vehicle-turnout coupled dynamics model was established to evaluate dynamic responses, and the reliability of the proposed model was verified by comparing with the testing data. The influence of worn curved switch rail on the running safety and stability was proposed. Conclusions include: (1) According to field testing, lateral acceleration of train body reached 0.8 m/s2 and −0.5 m/s2 in the diverging route; (2) Simulation results show that the dynamic performance in the switch panel has a significant effect on the running quality, and abnormal wear of curved switch rails leads to lateral acceleration increasing from 0.71 m/s2 to 1.34 m/s2, which makes vehicle transverse sway drastically; (3) Wheel-rail friction coefficient affects the development of rail wear and the coefficient range of 0.35–0.40 is inappropriate in the turnout.