To further analyze the damage effects of projectile penetration into concrete targets and their influence on the penetration process, a systematic theoretical investigation was carried out. A spalling effect model was established based on the spalling phenomenon observed during normal perforation of concrete targets by projectiles. By integrating this model with the cratering effect model and the target resistance function, a theoretical model for penetration that comprehensively accounts for both cratering and spalling effects was developed. By means of the presented model, the influence of target thickness and impact velocity on the penetration process and target damage parameters were analyzed. The results show that as the concrete target thickness decreases or the impact velocity increases, the influence of the spalling effect on penetration resistance and residual velocity diminishes, while the proportion of the splash zone during the spalling stage increases, making the splash effect the dominant factor affecting resistance in the spalling stage. When the target thickness exceeds 4.5 times the projectile diameter, the influence of the spalling effect on the residual velocity exceeds 10%, rendering the spalling effect non-negligible. Cratering depth increases linearly with thickness when the thickness is not more than 4 times the projectile diameter, and then tends to stabilize. Spalling depth increases linearly with thickness when the thickness is not more than 6.9 times the projectile diameter, and then decreases linearly. During the linear increase stage, both cratering depth and spalling depth are approximately half of the concrete target thickness. Compared with perforation of 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. The proposed model effectively characterizes the damage effects of concrete targets and can provide a theoretical basis for penetration analysis and protective design of concrete targets.