Abstract: To further enhance the ride comfort and curve passing speed of high-speed rail vehicles, this study investigates the active control principles of vertical dampers in secondary suspension and proposes a multi-objective coordinated control method for the vertical vibration and roll motion of the carbody. A simplified vertical dynamic model of the vehicle was established, and a sliding mode surface was designed to address the vertical, pitch, and roll modes of the carbody. The main control force expression was derived based on the sliding mode control theory. A disturbance observer was constructed to estimate the partial state feedback, and the stability of the control system was proven. Subsequently, a three-dimensional nonlinear dynamic model of the vehicle system was established using SIMPACK, while the controller and actuators are implemented in MATLAB/SIMULINK, enabling co-simulation of dynamics and active control. The control effectiveness of carbody roll is investigated, and the effects of active vertical damping control on the ride comfort under typical track irregularities are analyzed. Numerical simulations indicate that the designed active vertical suspension configuration and sliding mode control theory can significantly reduce vertical acceleration below 10 Hz and drop the Sperling index, outperforming conventional skyhook damping control and passive suspension. The use of sliding mode control also enables active carbody roll motion control on curved tracks, reducing unbalanced centrifugal forces and substantially enhancing ride comfort, achieving control effects comparable to those of tilting trains. Although the active carbody roll control slightly increases safety indicators such as the derailment coefficient, these remain within safe limits with sufficient margins. The active vertical damping control can simultaneously address vertical vibration and roll motion control of the carbody, thereby further improving ride comfort both on tangent and curved tracks.