Abstract: Seismic tomography is one of commonly-used geophysical inversion method, which has been widely used in many fields and has achieved good effect. This paper introduces seismic tomography: including model parameterization, ray tracing and seismic travel-time calculation, nonlinear equation linearization, solving linear equations and evaluation of the solution. The P wave velocity structure of the two cross profiles has been obtained in Xiuyan crater, using seismic refraction data obtained by Geophysical Exploration Center, China Earthquake Administration. The results show that it is a simple crater, with a diameter of about 1.8 kin, and depth about 700 m The higher velocity of 7.0 km/s appearing at the depth of about 700 m indicates that the high temperature and high pressure formed by meteorites colliding make the rock melting, and change the nature of the surrounding rock, causing the velocity of surrounding rock increasing.