Fused　deposition　modeling　(FDM)　3D　printing　has　the　advantages　of　a　simple　molding　principle,　convenient　operation,　and　low　cost,　making　it　suitable　for　the　production　and　fabrication　of　complex　structural　parts.　Moving　forward　to　mass　production　using　3D　printing,　the　major　hurdle　to　overcome　is　the　achievement　of　high　dimensional　stability　and　adequate　mechanical　properties.　In　particular,　engineering　plastics　require　precise　dimensional　accuracy.　In　this　study,　we　overcame　the　issues　of　FDM　3D　printing　in　terms　of　ternary　material　compounds　for　polyamides　with　gradient　structures.　Using　multi-walled　carbon　nanotubes　(MWCNTs)　and　boron　nitride　(BN)　as　fillers,　polyamide　6　(PA6)-based　3D-printed　parts　with　high　dimensional　stability　were　prepared　using　a　single-nozzle,　two-component　composite　fused　deposition　modeling　(FDM)　3D　printing　technology　to　construct　a　gradient　structure.　The　ternary　composites　were　characterized　via　DSC　and　XRD　to　determine　the　optimal　crystallinity.　The　warpage　and　shrinkage　of　the　printed　samples　were　measured　to　ensure　the　dimensional　properties.　The　mechanical　properties　were　analyzed　to　determine　the　influence　of　the　gradient　structures　on　the　composites.　The　experimental　results　show　that　the　warpage　of　pure　polymer　3D-printed　parts　is　as　high　as　72.64%,　and　the　introduction　of　a　gradient　structure　can　reduce　the　warpage　to　3.40%　by　offsetting　the　shrinkage　internal　stress　between　layers.　In　addition,　the　tensile　strength　of　the　gradient　material　reaches　up　to　42.91　MPa,　and　the　increasing　filler　content　improves　the　interlayer　bonding　of　the　composites,　with　the　bending　strength　reaching　up　to　60.91　MPa　and　the　interlayer　shear　strength　reaching　up　to　10.23　MPa.　Therefore,　gradient　structure　design　can　be　used　to　produce　PA6　3D-printed　composites　with　high　dimensional　stability　without　sacrificing　the　mechanical　properties　of　PA6　composites.