Continuous　fiber　reinforced　variable　stiffness　composite　structures　can　adjust　fiber　content　and　direction　distribution　to　maximize　fiber　performance　advantages.　However,　the　existing　manufacturing　process　is　difficult　to　precisely　control　the　fiber　content.　The　mapping　relationship　between　process　parameters　and　fiber　content　is　established　based　on　3D　printing　of　the　continuous　fiber　reinforced　composites.　The　integrated　manufacturing　of　continuous　fiber　reinforced　variable　stiffness　composite　structures　is　achieved　by　dynamically　adjusting　the　feed　ratio　of　resin　during　the　3D　printing　process.　The　influence　of　the　variable　stiffness　distribution　of　fiber　content　on　the　bending　and　impact　properties　of　the　part　is　systematically　studied.　The　flexural　modulus　and　impact　strength　of　the　3D　printed　variable　stiffness　structures　are　respectively　70%　and　65%　higher　than　that　of　the　homogeneous　structures　under　the　same　average　fiber　content.　The　failure　behavior　of　3D　printed　continuous　fiber　reinforced　variable　stiffness　composite　structures　is　analyzed　by　constitutive　models　of　3D　printed　composites　with　different　fiber　content.　The　results　show　that　the　resistance　of　the　part　to　fiber　tensile　damage　will　increase　by　setting　a　higher　fiber　content　on　the　back　side　of　the　part,　and　the　load-bearing　capacity　of　the　part　and　the　use　efficiency　of　the　fiber　will　be　greatly　improved.　The　research　in　this　paper　provides　new　ideas　for　the　design　and　manufacture　of　composite　materials　in　the　aerospace,　rail　transit　and　other　fields.　©　2022　Journal　of　Mechanical　Engineering.