Considering direct interaction of the projectile with the steel bar, the approximate model of the projectile penetrating into the reinforced concrete is established. Using this model, the acceleration-time history is obtained. Calculation data are in agreement with experimental data. The model is used to analyze the effect of steel bar size, steel bar mesh size and steel bar configuration on the penetration depth and the overload effect in penetration process. The results indicate that when the projectile penetrates into the reinforced concrete targets at the intersection of the steel bar, the steel bar mesh size and steel bar size have an important influence on the penetration; when the projectile has small kinetic energy, the first layer of steel consumes most of kinetic energy. On the other hand, no matter how much the steel bar mesh size is, part of kinetic energy is used up by the first layer of steel when the projectile has large kinetic energy.