The　paper　studies　comparatively　on　the　microstructures　and　mechanical　performances　at　elevated　temperature　of　SLM-fabricated　Inconel　718　alloy　in　as-build,　SHT　980,　SHT　1080,　SHT　980　+　1080　heat　treated　conditions.　The　morphology　and　distribution　of　delta　phase　in　the　gamma　matrix　are　regulated　by　pre-designed　heat　treatment　schemes,　their　effects　on　tensile　properties　and　stress　rupture　properties　at　elevated　temperature　are　discussed.　The　results　show　that　the　specimens　of　SLM-fabricated　Inconel　718　alloy　in　SHT　980　+　1080　heat　treated　conditions　possess　the　optimum　mechanical　performances　at　elevated　temperature,　in　which　the　morphology　and　distribution　of　delta　phase　in　the　gamma　matrix　are　the　key　factors　in　determining　their　high　temperature　performances,　The　excessive　delta　phases　within　grains　and　along　grain　boundaries　can　easily　lead　to　dislocation　piling　up　in　the　process　of　tensile　test　at　elevated　temperature,　causing　local　stress　concentration　and　microcrack　generation　in　the　matrix,　further　initiating　premature　failure　of　parts.　However,　lack　of　delta　phase　will　reduce　the　high　temperature　strength　of　grain　boundaries　and　then　influence　the　high　temperature　mechanical　properties.　As　a　result,　the　suitable　heat　treatment　is　used　to　regulate　the　precipitation　of　delta　phase　and　the　moderate　amount　of　delta　phases　precipitate　along　grain　boundaries,　further　improving　high　temperature　mechanical　properties　of　IN718　alloy.