This　paper　investigates　the　correlation　between　the　surface　quality　and　the　cross-sectional　quality,　microstructure,　internal　defects,　and　mechanical　properties　of　specimens　formed　by　selective　laser　melting　(SLM)　under　different　scanning　speeds　and　scanning　intervals.　Therefore,　different　machining　parameters　were　chosen　to　prepare　titanium　alloy　specimens　by　SLM　technique.　The　surface　morphology　of　the　specimens　was　characterized　using　a　light　microscope,　and　the　surface　quality,　microstructure,　internal　defects,　and　deep　connection　of　the　mechanical　properties　of　the　specimens　formed　under　different　parameters　were　investigated.　In　addition,　numerical　simulation　of　the　melt　pool　morphology　under　different　scanning　speeds　was　used.　The　results　show　that　there　is　a　strong　correlation　between　the　surface　quality　of　the　specimen　and　the　section　quality　and　mechanical　properties.　When　the　scanning　speed　is　350　mm/s,　the　surface　roughness　is　14.7　mu　m,　the　density　is　99.99%,　the　tensile　strength　and　yield　strength　are　1209　and　1151　Mpa　respectively,　and　the　surface　quality,　cross-sectional　quality　and　mechanical　properties　all　tend　to　deteriorate　as　the　scanning　speed　increases.　When　the　scanning　interval　is　0.11　mm,　the　mechanical　properties　of　surface　quality　and　cross-sectional　quality　are　optimal,　the　surface　roughness　is　14.5　mu　m,　and　the　density　reaches　99.99%,　at　this　time,　the　microscopic　needle　martensite　alpha　＇　phase　is　uniformly　distributed　and　refined,　and　its　mechanical　properties　are　optimal,　the　tensile　strength　is　1239　MPa,　and　the　internal　hole　defects　are　less.　Numerical　simulations　of　a　single　track　melt　pool　show　that　the　depth　of　depression　caused　by　the　recoil　pressure　is　larger　and　the　melt　pool　is　deeper　when　the　scanning　speed　is　350　mm/s.　Therefore,　it　has　better　fluidity　and　ductility.　Simulation　results　of　the　double　tracks　show　that　when　the　scanning　interval　is　130　mu　m,　a　large　amount　of　incompletely　melted　powder　at　the　midline　of　the　double　track　does　not　lap　well,　which　leads　to　the　formation　of　pore　defects　inside　the　specimen.　The　above　simulation　results　are　highly　consistent　with　the　surface　quality　of　the　specimens　during　the　experiments,　which　provides　a　guide　to　analyze　the　connection　between　the　melt　pool　evolution　and　the　Ti6Al4V　molding　quality.