Abstarct: Reinforcement of composite structures affected by the explosive shock has a significant importance in the design of armors. In this research, a numerical finite element analysis has been carried out by using the LS-DYNA hydrocode for modeling the explosion phenomenon and its effect on the structure in the medium of the water and the air. The composite structure in this study consists of three laxyers: an alumina ceramic plate (SiC), an intermediate plate of hot rolled steel (RHA) and a lower laxyer of polymethyl methacrylate (PMMA), which was used as a target laxyer. The shock wave was created by blasting of a spherical explosive charge that located at different distances from the center of the structure surface, and in an intermediate medium hits to the structure. A three-dimensional simulation was carried out in the air medium by Load Blast Enhanced (LBE) method, and in the water medium by an Arbitrary Lagrangian-Eulerian (ALE) method. For the verification of the model as well as the analysis of the accuracy in both intermediate environments, the numerical results were compared to the other empirical studies. In the air blasting, the impact of a uniform and nonuniform shock wave on the perpendicular stress and displacement of the target laxyer were investigated. The response surface method (RSM) was used to achieve the optimal structure, which transmitted the least stress and displacement to the target laxyer along with the light weight. By using the second order regression model, the stress and deformation function in the target laxyer was created and the optimal thickness of laxyers was predicted. Similarly, in the water media, the effect of the collision shock created from different stand-off distances on the displacement and the amount of stress of the target laxyer as a response was investigated. Finally, in the same structure at both air and water media, results were compared together. This comparison showed that the exerted deflection and stress on the target laxyer in underwater explosion was significantly higher than those of air medium. The reason for this phenomenon was the higher shock wave velocity due to higher density of water versus the air, and also higher amount of water contribing in the deformation process.