In this paper, the behavior of concrete subjected to eroding penetration of projectiles is studied. Based on qualitative similarities of eroding penetration at metallic and concrete targets, plastic flow of the particles around the projectile tip in a concrete target is illustrated. Based on visco-plastic behavior of concrete, changes on the plastic field of the target at Walker-Anderson model is made in order to analyze eroding penetration into concrete. Since there is not any analytical model and standard tests for eroding long rod (9≤L/d≤11 and 11gr<m<9gr) penetration into the concrete, 52 high velocity penetration tests were designed and carried out. Furthermore, with solving the final equations of the Forrestal model, penetration depth of eroding projectiles is calculated. Comparison between the results of the improved Walker-Anderson model and the Forrestal model showed that although the Forrestal model is a comprehensive model in rigid penetration, using it for assessment of eroding penetration into concrete is completely wrong. Besides, the improved Walker-Anderson model can analyze this phenomenon satisfactorily.