The ventilated cavitation is first predigested to be an air suspension, and then, based on the theory of added mass and air suspension, the FSI vibration equation of ventilated cavitating underwater vehicles is deduced. The change of natural frequency of underwater vehicle, which is enwrapped by ventilated cavitation of different length, is computed, and the influences of ventilated cavitation on vibration of underwater vehicles are investigated. Based on these, the response of structure, impacted by a transverse force, has been analyzed. The results reveal that the natural frequency of structure increases wavily as well as the increment of the length of ventilated cavitation. It is also found that the first step mode frequency is influenced mostly by the elasticity of ventilated cavitation, besides, the influence of ventilated cavitation becomes weaker with the increase of mode step; Under the impact force, the response of amplitude becomes smaller and the response of frequency becomes bigger with the increment of the length of ventilated cavitation.