This paper has dealt with the seismic reflection tomography, which is based on Fermat’s principleand, using the pre-stack data, inverts the underground structure layer by layer. In this method, various stratigraphic interfaces are regarded locally as planes. With the use of estimated parameters such as interface and velocity, the imaging of the whole section can be achieved merely by making repeated localized inversion. With this method, two seismic profiles in the Sanbanxi hydropower station were processed, and the results are quite consistent with theborehole data.