For　the　further　application　of　selective　laser　melting　(SLM)　AlSi10Mg　alloy　in　aerospace,　the　microstructure　and　mechanical　properties　of　SLM　AlSilOMg　alloy　at　room　temperature,　200　°C，and　300　°C　were　analyzed　based　on　the　self-developed　in-situ　SEM　high-temperature　tensile　test　stage,　and　the　fracture　mechanism　was　summarized.　Results　show　that　the　microstructure　of　SLM　AlSilOMg　alloy　was　composed　of　a-Al　matrix,　eutectic　Si,　and　plenty　of　pores,　and　eutectic　Si　distributed　uniformly　in　the　a　-　A1　matrix　with　a　continuous　network　structure.　With　temperature　increasing,　the　yield　strength　and　ultimate　tensile　strength　of　SLM　AlSilOMg　alloy　decreased　from　207　MPa　and　304　MPa　at　room　temperature　to　52　MPa　and　71　MPa　at　300　°C　，whereas　the　elongation　increased　from　7.　4%　at　room　temperature　to　59.　5%　at　300　°C.　No　evident　necking　behavior　of　specimen　was　observed　at　room　temperature　during　the　tensile　test.　As　the　temperature　increased，the　necking　behavior　became　obvious，which　suggests　that　the　specimen　experienced　more　sufficient　plastic　deformation.　Moreover,　the　fracture　position　of　the　specimen　more　and　more　deviated　from　the　center　of　the　marking　section　with　increasing　temperature.　By　analyzing　the　deformation　behavior　of　specimen,　it　was　found　that　at　200°C　intracrystalline　deformation　was　dominant　and　intracrystalline　slip　occurred,　while　at　300°C　the　slip　was　mainly　at　grain　boundary,　which　resulted　in　grain　boundary　slip.　Since　there　were　a　large　number　of　defects　inside　and　on　the　surface　of　the　specimen,　the　fracture　mechanism　of　SLM　AlSilOMg　alloy　was　the　quasi-cleavage　fracture　caused　by　the　microstructure　change　at　the　molten　pool　boundary　combined　with　the　connection　of　pores.　With　the　increase　in　temperature,　due　to　the　stress　concentration　at　the　edge　of　the　initial　pores，new　void　nucleation　was　generated，and　the　new　void　nucleation　was　connected　with　adjacent　pores，leading　to　the　final　fracture　of　the　specimen.　©　2022　Harbin　Institute　of　Technology.　All　rights　reserved.