Abstract:The near-surface velocity structure can be obtained by first calculating ray path of first break travel-time passing through a velocity model by using finite-difference method for Eikonal equation and then by conducting travel-time inversion using introducing a priori geologic information and orthogonal constrained least square decomposition. The tomographic approach which basic unit is rectangular block can model and inverse the complex velocity structure. It doesn't have to identify wave-form and can calculate quickly. Inversion results for real data show that there is strong lateral variation in near-surface velocity when the near-surface condition is complex and that resulted image on stack section is more clear after tomographic inversion.