In　this　study,　nanoscale　welding　quality　and　morphology　changes　of　multi-walled　carbon　nanotubes　are　investigated　by　changing　laser　wavelengths　and　the　irradiation　time.　Lasers　with　1064　nm　and　355　nm　are　used　in　our　experiments.　The　1064　nm　laser　can　lead　to　nanowelding　with　good　quality,　while　the　355　nm　laser　changes　the　curvature.　The　experiments　demonstrate　that　the　morphology,　structures　and　the　welding　quality　can　be　adjusted　by　changing　laser　wavelengths.　In　this　letter,　the　dynamic　process　of　nanostructures　changing　is　studied　by　changing　the　irradiation　time.　The　experimental　results　show　that　the　morphology　and　structures　can　be　controlled　by　adjusting　the　irradiation　time.　The　detailed　dynamic　process　of　nanostructures　changing　confirms　the　formation　mechanism　of　nano-welding　and　the　thermal　effects　during　the　process.