Abstract: Based on the overlapping grid technique, VOF (Volume of Fluid) multiphase flow model and improved delayed detached eddy, a numerical method is established to reduce the load and increase the stability of double vehicles under active ventilation. And it analyzes the influence of ventilation on cavity morphology, load characteristic and motion stability. After the ventilated cavity completely encloses the region below the orifice of the vehicle, the amplitude and an alternating peak of the transverse load decrease with the increase of the certain ventilation capacity. At the same time, the deflection torque can greatly reduce the flow interference in the narrow flow field between double vehicles. To avoid resonance, the natural frequency of the vehicle should be kept outside the low-frequency range generated by the ventilation effect. Therefore, active ventilation technology can improve the motion instability of multiple vehicle salvos.