The　removing　and　adding　materials　using　laser　beam　have　been　both　applied　widely　in　manufacture　of　micro　parts.　But　less　attention　has　been　focused　on　a　fabricating　technology　combining　removing　and　adding　materials.　Induced　by　the　irradiation　of　laser　beam,　marginal　metal　powders　are　sintered　together　into　thin　walls　along　laser　traces　with　central　metal　particles　vaporized　and　sputtered.　In　the　paper,　the　variation　of　the　microstructure　of　vaporizing　and　melting　components　in　this　process　is　studied　quantitatively.　The　profile　of　sintering　walls　and　thermal　expansion　grooves　were　measured　by　an　optical　microscope,　while　the　speed　of　thermal　diffusion　was　detected　by　high　speed　schlieren　photography.　The　characteristics　of　micro　melting　and　vaporizing　induced　by　laser　beam　are　further　discussed　and　the　mechanism　of　microstructure　of　metal　powders　is　explored.　It　is　observed　that　the　stress　generated　by　the　thermal　diffusion　is　a　critical　factor　influencing　the　quality　of　sintering　thin　walls.