In　the　paper,　the　effects　of　porosities　and　average　particle　sizes　of　powder　layer　on　light　absorption　during　SLM　process　were　investigated,　in　which　closed-packing　models　based　on　Horsfieled＇s　filling　method　were　established　and　light　absorption　was　simulated　using　ray　tracing　based　on　laser-material　interaction　mechanism.　Corresponding　to　closed-packing　models,　the　powder　materials　were　prepared　for　absorption　measurement　using　integrating　sphere.　The　experimental　results　of　light　absorption　verify　the　feasibility　of　the　establishment　of　closed-packing　models,　the　accuracy　in　calculation　in　the　light　absorption.　The　results　show　the　absorption　of　powder　layer　of　Ti6Al4V　alloy　is　higher　than　70%.　The　decrease　of　porosity　of　powder　layer　benefits　to　improve　the　absorption,　while　the　absorption　tends　to　decrease　if　porosity　decreases　to　a　certain　value　due　to　the　reflection.　The　decrease　of　average　particle　size　of　powder　particles　benefits　also　to　improve　the　absorption.　If　the　light　irradiates　at　positions　with　different　particle　arrangements,　the　absorption　behavior　changes　with　irradiation　condition　whether　there　occurs　the　multi-reflection.　The　above　research　provides　theoretical　basis　for　preparation　of　new　powder　materials,　their　parameter　developing　for　SLM　technology　and　even　the　properties　regulation　of　SLM　fabricated　component.