It　is　important　and　necessary　to　understand　the　micro-mechanism　of　rhenium　(Re)　effect　in　the　deformation　process.　The　in-situ　tensile　experiments　of　Ni-Al　and　Ni-Al-Re　model　single　crystal　superalloys　have　been　carried　out　in　scanning　electron　microscope　at　750　degrees　C.　It　is　found　that　Re　can　promote　the　complex　stacking　fault　(CSF)　formation,　which　is　similar　to　the　previous　results　after　tensile　experiments　at　room　temperature.　The　micro-mechanism　of　Re　promoting　the　CSF　formation　has　been　investigated　by　means　of　advanced　probe-corrected　scanning　transmission　electron　microscopy　and　energy　dispersive　X-ray　spectroscopy.　The　local　high　concentration　of　Re　is　observed　at　CSF　regions　after　tensile　experiments　both　at　room　temperature　and　750　degrees　C.　The　first　principles　calculation　results　further　indicate　that　low　concentration　of　Re　increases　CSF　energy,　while　high　concentration　of　Re　decreases　CSF　energy,　which　is　consistent　with　the　experimental　results.　(C)　2020　Elsevier　B.V.　All　rights　reserved.