The　ultrashort　pulsed　(USP)　laser　microwelding　of　sapphire/lnvar36　alloy　controlled　by　the　surface　roughness　of　metal　was　investigated　for　the　first　time.　The　surface　roughness　(S-a)　of　Invar　alloys　gradually　decreased　from　0.944　to　0.029　mu　m　from　the　prime　surface　to　grounded　and　polished　surface.　However,　the　joint　shear　strength　first　increased　and　then　decreased　with　the　lowered　S-a,　the　maximum　shear　strength　reached　107.87　MPa　at　the　S-a　similar　to　0.131　mu　m.　Compared　to　other　surfaces　with　low　S-a,　the　relatively　high　surface　roughness　enhanced　the　interfacial　thermal　deposition　both　spatially　and　temporally　which　in　turn　promoted　the　diffusion　of　interface　elements　and　the　formation　of　jagged　mechanical　interlocking　structures.　Therefore,　the　appropriate　rough　metal　surface　was　beneficial　for　the　enhancement　of　sapphire/metal　dissimilar　joints.　This　report　is　of　great　significance　in　simplifying　the　surface　preparation　process　in　the　USP　laser　microwelding　of　transparent　hard　and　brittle　materials　with　metals,　therefore　promoting　this　technique　from　lab　to　industry.