Abstract: To further analyze the damage effects of projectile penetration into concrete targets and their influence on the penetration process, this study established a spalling effect model for normal projectile penetration based on the observed spalling damage phenomena. Subsequently, by integrating the target resistance function, a theoretical penetration model was developed. The cratering effect and the spalling effect were considered in the presented model. The reliability of the theoretical penetration model was verified using experimental data on crater depth, spalling depth, and residual velocity. Finally, based on this presented model, the influence of the concrete target thickness and initial impact velocity on the penetration process and the damage parameters of concrete targets were discussed. As the thickness increases, the influence of spalling damage on penetration resistance and the residual velocity becomes more pronounced, while the proportion of the splashing zone decreases during the spalling stage. When the thickness is less than 3d, the spalling zone is a splash zone. When the concrete thickness exceeds 4.5d, the influence of the spalling effect on the residual velocity exceeds 10%, rendering the spalling effect non-negligible. With increasing impact velocity, the influence of the spalling effect on penetration resistance and residual velocity decreases. Concurrently, the proportion of the splashing zone within the spalling stage gradually expands, causing the splashing effect to become the dominant factor governing resistance variations during spalling. With increasing concrete target thickness, the crater depth first increases linearly (thickness≤4d) and then stabilizes, while the spalling depth initially exhibits a linear increase (thickness≤6.9d) followed by a linear decrease. During the linear growth phase, both the crater depth and the spalling depth approximate half of the concrete target thickness. Compared to thin concrete targets, variations in impact velocity exhibit a more pronounced influence on the crater depth and spalling depth during the penetration of thick concrete targets.