This paper is aim to investigate the damage characteristics of a shallow-buried water diversion box culvert subjected to a surface explosion. For this purpose, the soil model is verified by comparing with the analytical formulas of the Technical Manual (TM5-855-1), and the accuracy of the reinforced concrete model is validated with a previous explosion test. Subsequently, a three-dimensional (3D) numerical model of the water diversion culvert is established. A fully coupled Eulerian and Lagrangian (CEL) approach is presented to model the soil-structure-water interaction. The shock wave propagation characteristics in the soil, culvert and water medium are captured. The dynamic responses and damage processes of the shallow-buried box culvert in design water diversion condition (i.e. unconfined full flow) subjected to surface explosion are investigated. Other three water diversion conditions (i.e. pressure flow, free flow and no water) are employed to evaluate the influence of the water diversion condition on the antiknock performance of the culvert. The effects of the burial depth and charge weight on the dynamic behavior of the culvert to surface explosion are also discussed. The results show that the surface blast loads will cause a great threat to the whole security of the shallow-buried water diversion box culvert. The water diversion condition has a significant influence on the dynamic behavior of the culvert when subjected to a surface explosion.