Based　on　theory　analysis　and　a　series　of　model　tests,　the　relationships　between　fiber　reinforced　polymer　(FRP)　strain　and　the　deflection/loading　were　discussed,　and　the　FRP　debonding　strain　was　also　analyzed.　The　results　show　that　FRP　strain　is　linear　to　the　deflection　of　RC　beam,　and　the　FRP　length　and　the　crack　of　concrete　or　the　failure　of　reinforcement　have　no　obvious　influence　on　this　rule.　FRP　can　reduce　the　ultimate　deflection　of　RC　beam,　while　the　ductility　of　RC　beam　strengthened　with　FRP　declines.　The　load-bearing　capacity　of　the　RC　beam　is　increased　by　FRP　with　large　amplitude　of　32%　in　this　test,　and　at　the　yield　point　of　steel　reinforcement,　the　increase　of　the　load-bearing　capacity　is　about　64%　of　the　total　increment.　FRP　ultimate　debonding　strain　is　about　8.117×10-3.　When　FRP　debonding,　the　deflection　of　RC　beam　is　1.01×10-3　L-3/h　(L　is　the　span　of　RC　beam,　h　is　the　height　of　RC　beam).　The　spans　of　the　service　bridges　are　larger　while　the　allowable　deflections　are　smaller,　so　FRP　strain　is　smaller.　As　a　result,　the　high　strength　performance　of　FRP　can　not　be　fully　exerted.