The　mechanical　properties　of　reinforced　concrete　(RC)　structures　are　damaged　and　degraded　after　exposure　to　fire.　To　investigate　the　mechanical　properties　of　high　temperature-damaged　RC　slabs　strengthened　with　carbon　fiber-reinforced　polymer　(CFRP),　a　three-dimensional　numerical　simulation　was　carried　out　based　on　the　＂thermal-stress＂　sequential　one-way　coupling　framework.Firstly,　the　heat　transfer　within　RC　slabs　under　high　temperature　was　simulated　to　obtain　the　temperature　field;　then,　considering　the　high　temperature-degradation　of　the　mechanical　properties　of　steel　and　concrete　materials　as　well　as　the　nonlinear　bond-slip　behavior　between　them,　assuming　that　the　interaction　between　external　CRFP　sheet　and　concrete　is　perfect　bond,　a　three-dimensional　finite　element　analysis　model　of　the　high-temperature　damaged　RC　slab　strengthened　by　CFRP　was　established.On　the　basis　of　verifying　the　rationality　of　the　three-dimensional　numerical　model,　the　failure　mode,　bearing　capacity,　deflection,　stiffness　and　internal　strain　of　the　CFRP-strengthened　RC　slabs　damaged　by　fire　exposures　of　varying　duration　were　analyzed,　and　the　strengthening　effect　was　evaluated.　The　influence　of　the　number　of　CFRP　sheets　on　the　strengthening　effect　was　further　discussed.　The　results　show　that　after　exposure　to　fire,　the　damage　pattern　of　RC　slabs　subjected　to　four-point　loading　is　the　typical　flexural　failure.With　the　increase　in　fire　exposure　time,　the　damage　of　RC　slab　is　more　and　more　serious　while　the　bearing　capacity　and　the　stiffness　are　reduced.Moreover,　the　strain　of　reinforcement　and　CFRP　has　increased.With　the　increase　of　CFRP　layers,　the　bearing　capacity　and　the　stiffness　of　damaged　RC　slabs　increase,　and　the　strain　of　reinforcement　and　CFRP　decreases.In　addition,　when　the　fire　exposure　of　slabs　reaches　the　fire　resistance　limit　(90　min),　the　bearing　capacity　of　the　slab　strengthened　with　two　layers　of　CFRP　can　be　restored　to　more　than　90%　of　that　in　the　sound　state.　©　2023,　The　Editorial　Board　of　Journal　of　Basic　Science　and　Engineering.　All　right　reserved.