Abstract: The principles and procedures of TBA method are described in detail.A dynamic muti-step finite element model is established to simulate excavation process of caverns in a hydropower station,and a calculation of getting mechanical parameter-field of surrounding rock has been done with the TBA method. The result is presented with numerical validation with GA.The elastic ratio rock is fixed effectively.The results show that the incremental displacements are consistent well with those measured ones.The distribution of parameters of rock mechanics is consistent with the real one.