This paper presents the procedure and the results of numerical simulations that are applied to an impact penetration test. As a result of an accidental explosion of an energy plant of a ship, such as a boiler or a turbine settled within an engine room, fragments may scatter with high speed and collide with wall plate. When fragments perforate through the wall plate around the engine room, the equipment and operators possibly be injured. A concept of protective wall gives one of the way to avoid such hazards. It is necessary to evaluate the protective capability of the wall, when designing the protective walls. First, an impact penetration test is carried out to evaluate the protective capability of a high tensile strength steel plate against the perforation failure. The test is performed with a powder accelerator to shoot the steel plate with a simulated fragment. The simulated fragment of a cylindrical shape is shoot with the speed of 413 m/s. Speeds of the fragment and a plug after perforation are measured by strain gauges and a high speed cinematograph during the test. Deformation of the fragment and the steel wall plate are also measured after the test. Next, numerical simulations are carried out to reproduce the experiment. DYNA3D code, a three dimensional elastic plastic large deformation impact contact problem analyzing program based on the finite element spatial discretization, is used to do numerical simulations of the test. The elastic-plastic model with failure is employed to express fracture phenomena occurred during the test. The fragment and the wall plate are assumed to be axially symmetric. The edge of the wall plate is fixed and the initial speed is applied to each grid of the fragment model. The speeds of the fragment and a plug after perforation are compared with the simulated values, changing parametrically the mechanical properties of the fragment and the wall plate. The effects of the mechanical properties on the speeds after perforation are obtained. As a result, a set of reasonable material properties is obtained by the numerical simulations. The experimental results are shown to be reproduced well by the numerical simulations with this set of material properties. The numerical simulation method is shown to be an efficient way to estimate the protection capability of a steel plate against the penetration caused by high speed fragments.