With increasing train speeds and the diversification of operating environments, optimizing the abnormal vibration of high-speed train tail cars has emerged as a critical challenge. In this study, aerodynamic and multi-body dynamic models of 3-car and 8-car train formations were developed to analyze the regulatory effects of vortex generators on the unsteady flow field, aerodynamic loads, and operational stability of tail cars at speeds of 200, 300, and 400 km/h. The results indicate that vortex generators narrow the airflow channel at the tail car’s streamline, thereby weakening the intensity of longitudinal vortices and reducing flow separation and the resultant negative pressure zones. At higher speeds, vortex generators can improve the pulsation intensity of various unsteady aerodynamic load components; however, at lower speeds, vortex generators may induce more severe lateral aerodynamic loads on the tail car. Regarding operational stability, the application of vortex generators significantly optimizes vertical stability across all speeds but adversely affects lateral stability at 200 and 300 km/h. Overall, the benefits of vortex generators are primarily realized in high-speed operations above 400 km/h, while their effectiveness in mitigating abnormal tail car vibration under lower speed conditions is relatively limited. These findings underscore the necessity of tailoring aerodynamic optimization strategies to specific speed regimes in high-speed rail operations.