A　3D　transient　finite　element　model　of　Inconel　718　nickel-based　superalloy　processed　by　selective　laser　melting　was　developed　to　study　the　heat　flux　in　the　molten　pool　under　the　condition　of　different　process　parameters　and　its　effect　on　the　temperature　field　and　the　shape　of　molten　pool,　in　which　a　solid　heat　transfer　module　and　a　laminar　flow　module　in　the　finite　element　simulation　software　COMSOL　Multiphysics　was　applied.　In　the　simulation　several　special　phenomenon　characterized　with　SLM　process　was　considered,　such　as　the　interaction　between　the　laser　and　material　with　stochastic　porosity　distribution　on　powder　bed,　and　the　nonlinear　change　of　thermophysical　properties　due　to　the　state　change　of　material　and　the　influence　of　the　Marangoni　effect　in　the　molten　pool.　The　results　show　that　the　Marangoni　effect　caused　by　the　surface　tension　of　molten　pool　makes　the　convective　heat　flux　play　a　leading　role　in　the　heat　transfer　process　in　the　molten　pool,　and　its　depth/width　ratio　is　changed　by　changing　the　magnitude　and　direction　of　the　heat　flow,　what　determines　the　shape　of　molten　pool.　The　increase　in　laser　power　or　reduced　scanning　speed　can　increase　the　heat　input　per　unit　time,　and　then　lead　to　a　Marangoni　convection　enhancement　within　the　molten　pool,　thus　enlarge　the　size　of　the　molten　pool.　The　experimental　results　are　in　good　agreement　with　the　simulation　results.