Reinforced concrete structures are frequently subjected to impact loads during their service life， leading to complex dynamic responses that are often difficult to predict. To systematically investigate the influence of concrete heterogeneity on the impact response and scaling effect of geometrically similar RC beams. Using a comparative analytical approach， three numerical models were established： a homogeneous RC beam （Homogeneity） and two heterogeneous RC beams （Heterogeneity-I and Heterogeneity-II）. The displacement， impact force， and reaction force were compared. Furthermore， damage modes， deflection curves， and energy absorption characteristics were analyzed to explore the intrinsic mechanisms of scaling effect. The results indicate that the concrete heterogeneity is one of the factors contributing to the scaling effect in the displacement of geometrically similar RC beams， while its influence on impact force and reaction force is relatively minor. The intrinsic mechanism of the above-mentioned phenomenon may be the difference in damage modes due to heterogeneity， which enhances the local response of the RC beams with analysis of deflection curves and energy absorption. Additionally， within the scope of this study， higher impact velocities lead to more pronounced scaling effect in the displacement. These findings provide theoretical insights for impact-resistant design of concrete structures and for similitude analysis in scaled experimental studies.