Abstract:Travel-time computation of seismic waves is kernel content realizing the prestack depth migration and seismic tomographic imaging, and its precision decides the final imaging effect. The method computing travel time of seismic waves by using finite-difference algorithm to solve eikonal equation has many advantages, which always finds favor in people's eyes. On the basis of method presented by predecessor that computing the time of first breaks at fourth point by eikonal equation when knowing the times of first breaks at three points, the paper presented a new algorithm that computes the time of first breaks at adjacent third point by eikonal equation when knowing the times of first breaks at two point and application of the method in combination with expanded wave-front method and local algorithm, which made the algorithm more robust.