A vortex generator (VG) can effectively prevent the airflow from separating prematurely and transfer the energy to the low-energy airflow at the bottom of the boundary layer so that it will not separate after obtaining energy and reduce the strength of the reverse vortex in the wake area to reduce the aerodynamic drag of the train. In this study, transient numerical simulations of VGs on China Railway CRH5 Size trains were conducted. The SST K–ω two-equation improved delayed detached eddy simulation turbulence model was used to solve the incompressible three-dimensional Navier–Stokes equations. The flow in the boundary layer was found, and the structure of the wake flow field at the rear of the train under different operating conditions was compared. The results showed that the arrangement of VGs at different locations in the tail car had a significant effect on the slipstream around the train, the train aerodynamics, and the flow field structure in the tail section. The placement of VGs at the bottom of the train reduced the slipstream, while the VGs placed on both sides of the glass and at the nose tip point increased the slipstream significantly. The VG could effectively reduce the pressure drag of the train, but had little influence on the shear drag of the train.