Numerical　simulation　is　an　effective　approach　to　analyze　the　selective　laser　melting　(SLM)　process　and　reduce　the　production　development　cost.　Based　on　the　finite　difference　method　(FDM),　the　nonuniform　grid　algorithm　(NUGA)　is　developed　to　simulate　the　thermal　behavior　in　SLM　process　concerning　the　variable　thermophysical　parameters　of　materials　with　different　status.　The　NUGA　can　effectively　improve　computing　efficiency,　and　the　calculation　speed　using　NUGA　is　6-10　times　than　that　without　using　NUGA.　Different　heat　transfer　strategies　are　used　on　each　side　of　the　two　critical　scanning　speeds,　68.95　mm/s　and　6895　mm/s,　respectively,　and　the　results　of　temperature　calculations　are　highly　consistent.　The　correctness　of　the　heat　transfer　strategy　under　different　speeds　is　analyzed　using　the　NUGA.　The　effects　of　processing　parameters　(laser　power,　scanning　speed　and　building　height)　on　the　shape　and　volume　of　the　molten　pool　are　investigated.　As　the　scanning　speed　ranged　from　100　mm/s　to　500　mm/s,　the　width　and　depth　of　the　molten　pool　decrease,　while　the　length　increases.　As　the　laser　power　ranged　from　100W　to　500W,　the　length,　width　and　depth　of　molten　pool　all　increase.　The　length　of　the　molten　pool　increases　11.68%　from　264.94　mu　m　of　layer　1　to　295.88　mu　m　of　layer　5.　The　molten　pool　volume　decreases,　then　increases　and　decreases　finally　from　the　start　to　the　end　of　single　molten　path.　The　molten　pool　volume　increases　with　increasing　laser　power　and　building　height,　while　decreases　with　increasing　scanning　speed　in　general.　The　NUGA　is　an　effective　method　for　temperature　simulation　of　large-size　parts,　which　expands　the　application　range　of　temperature　simulation　in　SLM　process.