Abstract: To improve the running stability of the trains, a new mixed control strategy is proposed based on the classical sky hook and acceleration-driven damping controls. The numerical simulation and hardware-in-the-loop experimental investigation on the control system of the high-speed train magnetorheological semi-active suspension are carried out, which verifies that the new mixed control strategy has a good control effect. Firstly, the mechanical characteristics of magnetorheological damper (MRD) are tested and analyzed, and a modified extended hyperbolic tangent model of MRD is established by introducing a modified function with current saturation characteristics. Then, a new mixed control strategy is designed to improve the running stability of the trains, and the proposed mixed control strategy parameters are determined. The control effects of different control strategies in the whole frequency domain are compared by analyzing the carbody acceleration transmission characteristics. Furthermore, the control advantages of the new mixed control strategy in the whole frequency domain are explained from the perspective of phase frequency characteristics. The modified MRD model is applied to the suspension control of the high-speed trains, and the joint simulation model of the vehicle magnetorheological semi-active suspension control system is established using UM software and Simulink software to analyze the influence of different control strategies on the vehicle's dynamic performance. Finally, a hardware-in-the-loop experimental table of the vehicle suspension system based on MRD is constructed, and the carbody response under different control strategies is analyzed through the hardware-in-the-loop experimental. The results reveal that compared with the traditional control strategy, the new mixed control strategy has a good control effect in low frequency and high frequency, which can not only improve the running stability of the trains, but also not deteriorate the running safety of the trains. The hardware-in-the-loop experiment proves the effectiveness of the new mixed control strategy and the feasibility of applying semi-active control suspension to high-speed trains.