The　strain　and　damage　self-sensing　properties　of　carbon　nanofibers　(CNFs)/flax　fiber-reinforced　polymer　(FFRP)　laminates　under　tension　were　investigated　via　simultaneously　measuring　the　changes　of　electrical　resistance　(ER)　and　acoustic　emission　(AE)　signals.　The　piezoresistive　mechanisms　together　with　the　damage　evolution　of　CNFs/　FFRP　laminates　were　also　explored.　The　results　revealed　that　both　ER　and　AE　responses　to　tensile　strains　in　CNFs/　FFRP　laminates　could　be　segmented　into　three　stages,　which　confirmed　their　good　damage　self-sensing　ability.　The　isochronous　and　reversible　electrical　resistance　responses　to　tensile　strains　proved　the　stability　and　repeatability　of　strain　self-sensing　capability　for　CNFs/FFRP　laminates.　Moreover,　in-situ　ER　measurement　is　sensitive　not　only　to　new　damages　but　also　to　existing　damages,　whereas　AE　signals　are　only　sensitive　to　new　damages.　Therefore,　adding　a　small　amount　of　conductive　CNFs　into　non-conductive　FFRP　laminates　could　provide　an　effective　strategy　to　achieve　the　self-sensing　ability　in　their　strain　and　damage　development.