Abstract: Based on Snell law and Femat principle, the two point ray tracing method for three-dimensional VSP was studied, and the calculating formulas of 3D segment iterative ray-tracing algorithm was given, then the iterative ray-tracing in three-dimensional medium was conducted by taking energy characteristics of the seismic ray into account.Multiwave forward modeling of deviated well in 3D complex medium was carried out.The results of modeling showed that this algorithm is fast and its calculating precision is high.