Abstract: Fluid structure coupling effect and dynamic load characteristics are the important basis of the safety evaluation of the vehicle in the process of underwater launching and floating ice break. In this paper, the main control parameters which influence the dynamic load and the stress at the head of the vehicle, as well as the similarity law, are obtained by dimensional analysis. Based on the LS-DYNA fluid structure coupling method, the numerical simulations for underwater launched vehicle impacting with floating ice have been conducted, and the load characteristics of the vehicle under the conditions of different impact velocities, different ice thicknesses and different ice sizes are obtained. The simulated results show that, the higher the initial velocity of the vehicle is, the greater the distinction of the influence of different ice targets on the overload and the stress at the head of the vehicle is, which is mainly due to the different destruction of different ice targets under the strong water impact generated by the underwater motion of the vehicle in the early stage. For the infinite ice sheet, when its thickness is more than 3 times the vehicle diameter, the penetration into the ice appears stable at the later stage, the rigid body acceleration and the stress at the head of the vehicle are only related to the penetration velocity and the dynamic mechanical properties of the ice; for the thinner ice target, the higher the velocity of the vehicle is, the smaller the stress at its head is. This is because the early damage of the ice under the water impact generated by the higher speed motion of the vehicle is more serious, the ice layer is easy to crack and bulge, resulting in the smaller stress at the vehicle head. For the broken ice whose radial dimension is 6 times the vehicle diameter, when its thickness is also greater than 5 times the vehicle diameter, the influence on the vehicle motion is almost the same as that of the infinite ice sheet; when its thickness is less than 3 times the diameter of the vehicle, the ice size effect can be ignored only when the vehicle velocity is low. In addition, by comparing the influence of broken ice and infinite ice on the vehicle motion, it can be observed that, the thicker ice got less damage by the water impact at the early stage, thus the influence of broken ice and infinite ice are basically the same; while the thinner ice is seriously damaged by the water impact, resulting in little influence of broken ice and infinite ice on the vehicle motion; only for the ice targets with medium thickness, their damage degrees are related to the radial size under the condition of the higher vehicle velocity, for instance, when the initial vehicle velocity is 40 m/s, there is a great damage difference between the two kinds of ice targets with dimensionless thickness 3 at the early stage, which leads to a significant difference in the influence on the vehicle motion at the later stage.