Abstract: 3D seismic numerical simulation can obtain the more realistic wavefield response of subsurface geologic bodies, but the computation amount is huge.During numerical simulation by using finite difference method,there are two ways to reduce computation amount,one is difference form design,the other is the selection of boundary condition.Starting from the principles of Perfect Matched Layer (PML) absorption boundary condition,the conventional attenuation functions of the PML artificial boundary conditions were summarized,and the importance of attenuation design was elaborated.Numerical simulation results indicate that the wavefield simulation result of cosine absorption is better than other absorption attenuation factors.