The　reduction　of　the　section　area　of　timber　beams　in　ancient　buildings　leads　to　the　decline　of　their　flexural　mechanical　properties.　In　order　to　study　the　effect　of　the　reinforcement　method　with　near-surface　mounted　CFRP　sheets,　three　groups　of　14　scaled　poplar　timber　beam　specimens　were　designed　for　static　loading　tests,　and　the　strengthening　effects　of　the　new　members　replacing　the　damaged　members　and　the　concealed　CFRP　sheets　strengthening　the　damaged　members　were　compared.　The　results　show　that　the　ultimate　flexural　capacity　and　flexural　stiffness　of　the　strengthened　timber　beams　are　significantly　improved　compared　with　the　simulated　damaged　beams;　the　bending　performance　of　the　optimum　strengthened　timber　beam　is　equivalent　to　that　of　the　undamaged　beam.　The　distribution　of　the　section　strain　of　the　strengthened　timber　beam　along　the　height　of　the　beam　section　basically　conforms　to　the　plane　section　assumption.　A　formula　for　calculating　the　ultimate　flexural　capacity　of　poplar　timber　beams　strengthened　with　CFRP　sheets　is　proposed.　The　calculated　results　are　in　good　agreement　with　the　experimental　results.　©　2023　-　IOS　Press.　All　rights　reserved.