In　this　paper,　the　diffusion　process　of　Cu3Sn/Cu　interface　in　lead-free　solder　joints　was　investigated　using　molecular　dynamics　(MD)　technique　with　the　modified　embedded　atomic　method　(MEAM)　potentials.　The　diffusion　behavior　of　different　atoms　was　analyzed　and　the　diffusion　activation　energies　was　obtained.　In　addition,　the　thickness　of　diffusion　transition　zone　was　acquired　based　on　the　empirical　equation　of　diffusion.　The　simulation　results　indicate　that　the　Cu　atoms　predominantly　diffuse　into　the　Cu3Sn　side　in　the　process　of　diffusion.　The　Cu　atoms　diffuse　slowly　but　deeply　diffuse　into　the　interior　of　Cu3Sn,　whereas　the　atoms　of　Cu3Sn　diffuse　with　high　rate　but　hardly　diffuse　into　the　interior　of　Cu.　Based　on　the　Arrhenius　relation　and　equation　of　Einstein,　the　diffusion　activation　energies　of　Cu　lattice　atoms　at　interface　is　172.76　kJ/mol,　and　the　Cu　and　Sn　atoms　in　Cu3Sn　lattice　are　52.48　and　77.86　kJ/mol,　respectively.　©　2017,　Editorial　Board　of　Transactions　of　the　China　Welding　Institution,　Magazine　Agency　Welding.　All　right　reserved.