Abstract: It starts in this paper from the fact that the ray-path satisfies the Fermat's principal in the whole ray-path. By use of one order Taylor expansion,a well-posed symmetry tridiagonal matrix equation that fits to approximately calculate ray-path adjustment is obtained.Then,combining solving this matrix equation and iterative technique,a whole-path iterative ray-tracing method is fulfilled.The procedure of the ray tracing is ended when the adjustments on the whole ray-path satisfy the preset precision.Numerical tests indicate that this algorithm is faster than traditional shooting method in the arbitrary interface velocity distribution and the precision can be predetermined.It offers a new kind of efficient ray-tracing method for seismic migration and tomography in complex structure.