Abstract:The method involves the following steps:One-order approximate formula that is suitable to obtaining reflection (refraction)points on any interface is taken according to the principle that a whole ray path satisfies same ray parameter.Segmentally-iterative operation,starting from any given initial ray path,is done to obtain reflaction (refraction) points on interface.On the basis of known ray path,reflection(refraction) points on the next interface segment are determined in the same way until we get to a whole ray.Ray tracing terminates when the revision values of reflection (refraction) points relating to a whole ray meet the accuracy requirements.Modeling computation shows that the method,whose accuracy varies with user's need,brings much faster operation than "target”method. The method,without ray blind area,can achieve accurate and fast seismic tomographic images for any interface.