Abstract: The Ray tracing method in the seismic forward modeling is to simplify the seismic wave theory into the ray theory,which belongs to a geometry seismology method, with the characteristics of convenient operation and good applicability. The main reservoir H3 sand interval in M oil and gas field is thin and rapidly changes in lateral. The post-drilling analysis showed that the interior sand bodies of H3 interval were possibly not connected between Well A and Well B. In order to confirm the complex geological structure between the wells, the authors built serval geological models,and conducted the seismic forward modelling through ray tracing method.The comparison of seismic profiles from the forward modeling and the real reveals that the connectivity of sand H3a, H3b, H3c of interval is poor among the wells, but H3d is possibly connective.