Additive　manufacturing　of　carbon-fiber-reinforced　polymer　(CFRP)　has　been　widely　used　in　many　fields.　However,　issues　such　as　inconsistent　fiber　orientation　distribution　and　void　formation　during　the　layer　stacking　process　have　hindered　the　further　optimization　of　the　composite　material＇s　performance.　This　study　aimed　to　address　these　challenges　by　conducting　a　comprehensive　investigation　into　the　influence　of　carbon　fiber　content　and　printing　parameters　on　the　micro-morphology,　thermal　properties,　and　mechanical　properties　of　PA6-CF　composites.　Additionally,　a　heat　treatment　process　was　proposed　to　enhance　the　interlayer　bonding　and　tensile　properties　of　the　printed　composites　in　the　printing　direction.　The　experimental　results　demonstrate　that　the　PA6-CF25　composite　achieved　the　highest　tensile　strength　of　163　MPa　under　optimal　heat　treatment　conditions:　120　degrees　C　for　7.5　h.　This　corresponds　to　a　significant　tensile　strength　enhancement　of　406%　compared　to　the　unreinforced　composites,　which　represents　the　highest　reported　improvement　in　the　current　field　of　CFRP-fused　deposition　3D　printing.　Additionally,　we　have　innovatively　developed　a　single-layer　monofilament　CF-OD　model　to　quantitatively　analyze　the　influence　of　fiber　orientation　distribution　on　the　properties　of　the　composite　material.　Under　specific　heat　treatment　conditions,　the　sample　exhibits　an　average　orientation　angle　mu　of　0.43　and　an　orientation　angle　variance　of　8.02.　The　peak　frequency　of　fiber　orientation　closely　aligns　with　0　degrees,　which　corresponds　to　the　printing　direction.　Finally,　the　study　explored　the　lightweight　applications　of　the　composite　material,　showcasing　the　impressive　specific　energy　absorption　(SEA)　value　of　17,800　J/kg　when　implementing　3D-printed　PA6-CF　composites　as　fillers　in　automobile　crash　boxes.