Abstract: Large-scale hydraulic engineering facilities, having multiple functions such as flood control, power generation, and irrigation, occupy a key position in the national infrastructure network. Their engineering characteristics and geographic features also render them potential targets for strikes. To clarify the damage modes of concrete gravity dams under different penetration positions, centrifuge tests on concrete gravity dams with internal explosions were conducted. Based on the Kong-Fang constitutive model of concrete materials and employing the Coupled SPG-Eulerian approach, a fully coupled numerical model of the explosive-dam-water reservoir system was developed. By integrating experimental and numerical findings, the failure modes of the concrete gravity dam were elucidated, and the damage characteristics under various penetration positions were analyzed. The optimal penetration position (i.e. the most unfavorable penetration position) under penetration explosive was identified, and a simplified dimensionless formula for determining this location was derived. The results indicate that under internal explosion loading, concrete gravity dams primarily undergo localized failure dominated by tensile damage, albeit with an overall trend of lateral "splitting" and vertical "cantilevering". The peak tensile stress and strain along the dam height (z-direction) can serve as characteristic parameters for damage assessment. For the 550 mm-high dam model under 80 g hypergravity conditions in this study, the optimal penetration position is found approximately 350 mm below the dam crest.