Abstract：Currently the perfectly matched layer(PML) absorbing boundary conditions were regarded as the best,however the routine PML absorbing boundary conditions have some disadvantages,such as too many variables,large calculation storage,complex programming,absorbing performance decreasing when the field source close truncated boundary.A non perfectly matched layer(NPML) absorbing boundary conditions which fit the acoustic wave equation was derived in this paper.Based on NPML and by using complex frequency expanding function,the wave equations in the PML medium were decomposed into normal term and attenuation term,and then the iteration refreshment was conducted individually.The analysis and experiment results show that when applying in the acoustic wave simulation the method not only has excellent absorption and attenuation performance,but also makes equation calculation simpler,programming easier and less memory needed for the PML auxiliary variables.
