Microstructural　evolution　of　the　heat-affected　zone　(HAZ)　seriously　affects　the　mechanical　properties　of　the　welded　joints.　In　this　paper,　QP980　steels　were　butt-welded　by　fiber　laser.　The　thermocouple　and　Gleeble1500　system　were　used　to　achieve　the　thermal　simulated　HAZ　specimens　of　laser　welded　joints,　which　solved　the　problem　that　it　was　difficult　to　evaluate　the　mechanical　properties　due　to　the　narrow　HAZ　of　the　laser　welding.　Large　amounts　of　granular　carbides　were　precipitated　in　the　block　martensite　of　the　sub-critical　HAZ　(SCHAZ).　Carbides　were　not　found　in　lath　martensite,　but　there　were　dislocation　tangles　in　the　lath　martensite　of　the　SCHAZ.　In　addition,　the　number　of　dislocations　in　the　ferrite　of　the　SCHAZ　was　significantly　reduced.　The　SCHAZ　had　the　lowest　strength　but　the　highest　elongation　owing　to　the　tempering.　The　fine-grain　strengthening　resulted　in　the　highest　tensile　strength　in　the　fine-grained　HAZ　(FGHAZ).　The　tensile　fracture　morphologies　indicated　a　brittle　fracture　mechanism　in　coarse-grained　HAZ　(CGHAZ)　and　FGHAZ,　and　exhibited　a　ductile　fracture　mechanism　in　the　inter-critical　HAZ　(ICHAZ)　and　SCHAZ.　According　to　the　overview　of　the　joint　and　the　local　mechanical　characteristics　of　HAZ,　the　numerical　model　of　the　tensile　test　was　performed　by　ABAQUS.　And　the　simulation　results　showed　good　agreement　with　the　experimental　results,　which　both　illuminated　the　constraint　effect　of　SCHAZ　and　made　the　strain　concentration　transferred　from　SCHAZ　to　the　BM　with　the　increase　of　stress.　©　2022　Elsevier　B.V.