To　improve　the　efficiency　and　accuracy　of　the　numerical　simulation　for　the　laser　powder　bed　fusion　(LPBF)　process,　an　optimized　segmented　heat　source　(OSHS)　model　is　proposed　in　this　work.　The　results　show　that　the　geometrical　size　and　temperature　distribution　contour　of　the　calculated　cross-sectional　molten　pool　are　almost　the　same　as　those　calculated　by　the　moving　heat　source　(MHS).　Under　the　same　mesh　scheme,　the　calculation　efficiency　of　the　OSHS　model　improves　about　9　times　to　that　of　the　traditional　MHS　model.　Moreover,　the　OSHS　model　can　achieve　stable　calculations　with　the　medium-size　elements　grid,　which　can　reduce　the　required　calculation　time　to　one-third　of　the　fine　mesh　scheme　and　achieve　almost　the　same　thermal-mechanical　calculation　result.　This　model　was　successfully　applied　on　the　simulation　of　the　LPBF　single　layer　multi-tracks　thermal　mechanical　numerical　simulation.　To　verify　the　calculated　results,　the　sample　of　the　same　size　was　prepared　using　316L　stainless　steel　by　LPBF　technology.　The　surface　residual　stress　components　of　the　as-built　sample　were　measured　by　X-Ray　Diffraction　(XRD).　The　calculated　residual　stress　curves　were　in　good　agreement　with　the　measured　results.　The　simulation　and　experimental　results　indicated　that　the　primary　surface　residual　stress　component　was　the　tensile　stress　along　the　laser　scanning　direction,　which　was　about　280　MPa.　The　shear　stress　was　concentrated　at　the　corners　of　the　as-built　sample.　Therefore,　the　OSHS　model　proposed　in　this　work　greatly　improved　the　calculation　efficiency　and　obtained　very　accurate　results　for　the　thermal-mechanical　simulation　of　the　LPBF　process.