Abstract: A kind of three-dimensional (3-D) sound ray tracing algorithm in heterogeneous media is studied. This algorithm includes two steps: wavefront traveltimes computation forward and sound ray tracing based on wavefront traveltimes backward. In forward step, we found on Eikonal equation and use GMM (Group marching method) wavefront marching method based on level set to compute wavefront traveltimes on discrete grid points step by step, beginning with sound source. In backward step, sound ray tracing is proceeded from receiver to each cell towards sound source in steps, with wavefront traveltimes computed in the forward step. Wavefront traveltimes on arbitrary positions in each cuboid cell can be expressed with linear interpolating function about wavefront traveltimes on grid points of the same cell. And so an algorithm of 3-D sound ray tracing in heterogeneous media is put forward. The simulation results indicate that this method can improve both precision and efficiency of 3-D sound ray tracing greatly.