<p>It is essential to study the mechanical behavior and dynamic response of projectiles penetrating targets for protection design and engineering applications. The smoothed particle hydrodynamics (SPH) method has been successfully applied in the numerical simulation of solid impacts. However, it still encounters several limitations, particularly the tensile instability. This paper proposes an improved SPH method that incorporates an adaptive reference configuration updating strategy to enhance simulation accuracy and stability in large deformation and damage scenarios. Moreover, to improve the computational efficiency of SPH in three-dimensional simulations, a GPU-based parallel acceleration strategy is also adopted. The improved SPH method is applied to scenarios involving projectiles penetrating steel plates and concrete targets. Comparisons with experimental data and the traditional SPH method demonstrate the advantages of the improved SPH method across several critical aspects, including residual velocity, material fracture, and debris generation. The proposed SPH method significantly enhances the numerical stability and accuracy of SPH, effectively capturing the failure characteristics of materials under impact loads and providing a more reliable numerical foundation for protection design.</p>