Selective　laser　melting　(SLM)　has　been　attracting　increasing　attention　as　a　suitable　route　for　fabricating　personalized　orthopedic　implants　to　address　patient-prosthesis　mismatches　and　has　been　used　for　producing　Co29Cr9W3Cu　alloys　in　our　previous　study.　However,　SLM　technology　can　result　in　the　formation　of　mesh-like　random　high-angle　grain　boundaries　(indicated　as　molten　pool　boundaries)　and　accumulation　of　residual　stress　in　the　microstructure,　possibly　causing　an　unstable　mechanical　property.　In　this　study,　the　research　on　the　relationship　between　microstructural　evolution　and　mechanical　properties　was　performed　on　the　SLM-produced　Co29Cr9W3Cu　alloys　with　different　heat　treatments　to　improve　the　reliable　mechanical　property　of　the　SLM-produced　Co29Cr9W3Cu　orthopedic　implants.　It　was　found　that　the　microstrucutre　with　mesh-like　random　high-angle　grain　boundaries　could　be　eliminated　during　recrystallization,　replaced　by　the　one　with　equiaxial　structure　containing　the　Sigma　3　grain　boundaries　(annealing　twin).　Most　importantly,　the　combined　effect　of　eliminating　the　mesh-like　random　high-angle　grain　boundaries　and　residual　stress　and　generating　the　Sigma　3　grain　boundary　contributed　to　an　increase　in　elongation　from　12.49%　of　the　as-SLM-produced　one　to　23.38%.　Proper　heat　treatment　is　considered　to　be　an　efficient　strategy　to　improve　the　mechanical　properties　of　the　SLM-produced　Co29Cr9W3Cu　alloy　with　a　desired　tensile　ductility.