Extremely　rapid　heating　and　cooling　rates　during　the　additive　manufacturing　(AM)　process　generate　complicated　thermal　cycles,　which　affect　the　microstructure　evolution　and　ultimate　mechanical　properties　of　the　alloy.　In　this　paper,　FGH96　blocks　with　a　height　of　6　mm　were　prepared　by　selective　laser　melting　(SLM)　and　the　microstructure　was　characterized　by　scanning　electron　microscopy　(SEM)　and　transmission　electron　microscopy　(TEM).　Comparing　specimens　of　varying　heights,　it　was　found　that　subsequent　thermal　cycles　(STC)　coarsened　some　solidified　grains　and　accelerated　the　grain　growth　along　the　build　direction,　together　with　an　increase　in　texture　intensity　and　high-angle　grain　boundaries　(HAGBs).　After　coarsening　the　grains　in　the　middle　portion　of　the　built　block,　finer　grains　were　observed　near　the　top　area　due　to　a　faster　cooling　rate.　There　were　numerous　dislocations　in　the　grain　because　of　the　occurrence　of　unequal　internal　tension.　In　the　middle　of　the　sample　with　stable　thermal　cycles,　the　dislocations　were　both　perpendicular　to　the　grain　growth　direction　and　45　degrees　off　it.　In　spite　of　the　texture　characteristics,　the　segregation　of　elements　was　also　found　to　be　influenced　by　thermal　cycling.　Inherent　reheating　leads　to　the　increase　in　the　Laves　phase　and　the　decrease　in　the　gamma＇　phase　as　subsequent　deposition.　This　was　also　one　of　the　reasons　why　the　microhardness　of　the　sample　decreased　as　the　building　height　and　the　other　reason　being　the　decrease　in　the　solution　treatment　of　the　later　sediments.