On basis of the existed TCK model, the establishment process of a new rock blasting damage model is discussed by considering the relationship of crack density Cd, which indicates the shock damage extent of rock, and sound wave attenuation coefficient ap. Then, this model is inserted into the user-defined material model library of ANSYS/LS-DYNA3D software to construct the new damage model. Numerical simulation of damage to retained rock mass of dam foundation caused by rock blasting excavation in dam region with this model. Calculation results show that: as far as the blasting parameters and geological conditions in this paper, the damage to retained rock mass below caused by rock blasting excavation above is basically limited to the scope of 1.5m below the bottom of blasthole, and damage degree gradually reduces from the bottom of blasthole to faraway. Meanwhile, blasting will not cause rock mass to open along soft layer inside, whose maximum calculation displacement is only 3mm. The calculation result can be referred by the practical engineering.