Abstract： Ｒock foundation excavation plays an important role in the entire project of hydraulic structures． The key and difficult point of the blasting excavation is how to reduce the damage of the rock mass on the foundation surface under the premise of ensuring the excavation of the structural foundation to the specified elevation． In this paper， ANSYS /LS-DYNA finite element software is used to numerically simulate the blasting damage of the rock mass 40 m underwater． The blasting and excavation simulation of composite energy dissipation structure，flexible cushion and traditional charge structure is carried out in a 24． 5 cm × 24． 5 cm × 30 cm rock mass model，respectively． Fluid-structure coupling algorithm is used in the simulation process，and 0． 4 MPa water pressure is added to simulate the 40 m water depth environment． The simulation results found that the damage depth of the basement，the energy transfer of the retained bedrock and the damage degree of the retained bedrock can be reduced by 38． 89%，30． 52%，and 30． 90% respectively by using the composite energy dispassion blasting technology under the same conditions． The results also show that the energy dissipation structure can effectively control the damage form and scope of the rock mass retained on the foundation surface，which can be applied to the protection of foundation surface of underwater rock excavation．