The　effect　of　deformation　temperature　on　tensile　behavior　of　Inconel　718　alloy　has　been　studied　by　a　self-developed　in-situ　high-temperature　tensile　stage　inside　a　scanning　electron　microscopy　at　a　temperature　range　from　room　temperature　(RT)　to　750　degrees　C.　The　dynamic　microstructure　evolution　and　mechanical　properties　at　different　temperatures　were　performed　and　compared　by　the　uniaxial　tensile　tests.　The　in-situ　test　results　showed　that　the　mechanical　properties　and　fracture　mechanisms　of　Inconel　718　alloy　were　sensitive　to　deformation　temperatures.　From　RT　to　650　degrees　C,　the　yield　stress　and　ultimate　tensile　strength　decrease　slightly　and　the　tensile　ductility　is　comparable.　While　up　to　750　degrees　C,　the　yield　stress　and　ultimate　tensile　strength　decrease　significantly,　the　elongation　and　reduction　of　cross　section　also　showed　a　significant　decrease　from　RT　to　750　degrees　C.　It　was　found　that　at　RT　and　650　degrees　C,　tensile　cracks　tended　to　initiate　around　the　carbide　particles　and　the　triple　junctions　of　grain　boundaries,　also　propagated　transgranularly;　at　750　degrees　C,　the　cracks　initiated　at　grain　boundaries　and　propagated　intergranularly.　In　fact,　with　the　increase　in　deformation　temperature,　the　fracture　mechanism　transformed　from　the　ductile　transgranular　fracture　to　the　brittle　intergranular　fracture.