Abstract: The stiffness and damping matrixes of 3D consistent artificial boundary are deduced through viscous-spring artificial boundary theory. 3D equivalent viscous-spring artificial boundary element is developed by comparing the matrixes of general finite element and consistent viscous-spring artificial boundary. This boundary element is applied to uniform and layered half space problems, respectively. The results show that 3D equivalent viscous-spring boundary element has the same precision as viscous-spring artificial boundary, and the former is more applicable and simple.