This paper mainly reviews the methods of seismic waves used to acquire subsurface velocity structures. Despite appearance of new approaches, seismic tomography, especially multi-phases grid tomography has been widely used and has been regarded as one of the effective methods to understand the interior structure imaging of the earth. Future requirement for the seismic tomography is to improve the quality of primary observation data, i.e. to increase the seismic stations used to receive the seismic waves. Meanwhile, multiple geophysical approaches along with restriction from inversion can establish a much strict geophysical model, which can decrease the geophysical inversion and interpretation ambiguity. This is not only the general trend of geophysical exploration and research but the direction of seismic tomography imaging.