Abstract: Aimed at the problems of large scale simulation and rapid calculation,as an effective and comprise means,2.5D numerical simulation balances simulation accuracy and calculation efficiency,instead of 3D numerical simulation.Based on L pattern 2.5D acoustic wave equation,a 2.5D acoustic wave equation numerical simulation from rugged topography with finite differential strategy is realized by the longitudinal coordinate transformation.The theoretical modeling results show that 2.5D acoustic wave equation numerical simulation can handle the rugged topography problem very well.Compared with the 2D acoustic wave equation numerical simulation results,they are consistent in kinematics characteristics of seismic wave while in dynamic characteristics of seismic wave the results of 2.5D coustic wave equation numerical simulation is superior.By the amplitude comparison of simulated recording for different offsets,the attenuation characteristics of 2.5D acoustic wave equation numerical simulation in time and space is verified.