Abstract: The seismic tomography technique is an important means to study the velocity structure of the strata, it is the method that combines the seismic wave travel or waveform data of the receiving point with the physical and mathematical model established to reconstruct the velocity structure of the strata. The accuracy of the forward modeling of tomography will directly affect goodness-of-fit of the reverse velocity relative to the true velocity of the stratum. Therefore, it is very important to find a higher precision forward modeling algorithm for tomography.Based on the three-dimensional layered medium, this paper will use the minimum traveltime ray tracing method by gridding model to conduct forward modeling research. In this paper, three grids of triangle, rectangle and hexagon will be used to parameterize the model, and then their forward results accuracy will be compared to summarize the optimal mesh division method for three-dimensional layered medium.