Abstract: The failure processes of fluid filled structures induced by the impact of high-velocity fragments with various impact velocities and length to diameter ratios were performed using the AUTODYN-2D hydrocode. Influences of these fragment factors on cavity radius, hydraulic impulse and deflection deformation of the tank were obtained. The result indicates that the energy transferring from a high-velocity fragment to a contained liquid is accomplished through pressure induced in the liquid by impact shock and projectile drag. Sequently, the cavity formed by the liquid motion continues to expand. And the energy leads to dangerous tensile stress levels at the tank walls, which results in the failure. Moreover, the hydrodynamic ram effects strongly depend on impact velocities and length to diameter ratios. In some conditions, the deflection deformation increases with the impact velocity, but decreases with the length to diameter ratios.