The　WC-Co　cemented　carbides　with　near　fully-dense　and　crack-free　microstructure　were　fabricated　by　the　laser　powder　bed　fusion　(LPBF)　process　and　a　subsequent　heat-treatment.　The　microstructures　and　mechanical　properties　of　the　as-printed　and　heat-treated　cemented　carbide　specimens　were　investigated　in　detail.　The　formation　mechanisms　and　control　method　of　the　microstructural　defects　in　LPBF　printed　cemented　carbides　were　proposed.　A　number　of　particles　of　2.5　nm-2.0　mu　m　formed　in　WC　grains　after　heat-treatment.　The　nano-sized　particles　have　a　coherent　interface　with　the　WC　matrix.　The　formation　mechanisms　of　the　particles　and　their　effect　on　the　enhancement　of　mechanical　properties　of　the　cemented　carbides　were　demonstrated.　Furthermore,　the　cutting　performance　of　the　LPBF　printed　cemented　carbides　inserts　was　tested　under　actual　working　conditions,　which　exhibited　excellent　service　properties　and　promising　application　prospects.