In　order　to　study　the　retrofitting　effects　of　hybrid　fiber　reinforced　reactive　powder　concrete　(HFRPC),　the　flexural　behaviour　of　reinforced　concrete　(RC)　beams　reinforced　with　HFRPC　was　investigated　by　experiment　and　theory,　then　compared　with　reinforced　concrete　beams　without　retrofitting.　Seven　test　beams　were　designed　and　made,　one　of　which　was　not　retrofitted,　while　the　other　6　were　retrofitted　with　HFRPC.　The　test　variables　include　thickness　of　HFRPC,　HFRPC　and　concrete　interfacial　bonding　method,　retrofitting　fiber,　and　so　on.　The　test　results　show　that　the　reinforced　concrete　beam　strengthened　with　HFRPC　exhibits　improved　bearing　capacity　and　decreased　deformation.　The　HFRPC　retrofitting　layer　bonds　well　with　concrete,　no　debonding　failure　happens.　While　there　are　numerous　cracks　on　the　HFRPC　reinforcement　layer,　crack　width　is　significantly　decreased.　Gouged　beams　have　larger　bearing　capacity　than　those　with　troughs.　The　superior　performance　of　high-strength　steel　set　in　HFRPC　is　fully　utilized.　Beams　with　a　40　mm　thickness　retrofitting　layer　have　larger　capacity　than　30　mm　beams,　about　5%　better　flexural　performance.　Adopting　fiber　cloth　wraps　to　retrofit　new　and　old　concrete　beams　can　effectively　prevent　crack　propagation,　and　thus　slowing　down　loss　of　ultimate　load　bearing　capacity.　Through　theoretical　analysis,　a　formula　for　the　calculation　of　HFRPC　beam　crack　load,　yield　load,　and　ultimate　load　is　provided.　Finally,　the　experimental　results　match　well　with　the　theoretical　predictions.　©,　2015,　Editorial　Board　of　Journal　of　HEU.　All　right　reserved.