Engineering regional geologic condition is an important factor that affects the stabilization of underground cavern group

while the common numerical analysis soft wares have some disadvantages such as the long time consumption for modeling

low accuracy and the difficulty in reflecting the real complex geological features. Aiming at these problems

a mixed data structure， in which nonuniform rational B-spline(NURBS) is predominated，is used to carry out the 3D detailed modeling of the complex regional geological structure; and the whole 3D refined geological model of a large underground cavern group in Southwest China is established by this method. Based on this geological model

a numerical model including complex geological factors such as the space surface faults

formations have also been built; and combine the implicit and explicit module of ABAQUS

the underground cavern group excavation and dynamic response under seismic load have been simulated. The results indicate that: This approach not only reflects the actual geological condition to the greatest degree

but also makes against the mesh generation and numerical calculation; thus it provides an accurate and practical model for the dynamic response analysis of underground cavern group and important technical support for the seismic safety evaluation of underground cavern group.