After　a　brief　review　of　studies　on　artificial　boundaries　in　dynamic　soil-structure　interaction,　a　three-dimensional　viscous-spring　artificial　boundary　(VSAB)　in　the　time　domain　is　developed　in　this　paper.　First,　the　3D　VSAB　equations　in　the　normal　and　tangential　directions　are　derived　based　on　the　elastic　wave　motion　theory.　Secondly,　a　numerical　simulation　technique　of　wave　motion　equations　along　with　the　VSAB　condition　in　the　time　domain　is　studied.　Finally,　numerical　examples　of　some　classical　elastic　wave　motion　problems　are　presented　and　the　results　are　compared　with　the　associated　theoretical　solutions,　demonstrating　that　high　precision　and　adequate　stability　can　be　achieved　by　using　the　proposed　3D　VSAB.　The　proposed　3D　VSAB　can　be　conveniently　incorporated　in　the　general　finite　element　program,　which　is　commonly　used　to　study　dynamic　soil-structure　interaction　problems.