This　paper　presents　experimental,　numerical　and　analytical　investigations　to　evaluate　the　compressive　behavior　and　size　effect　of　square　concrete　columns　internally　reinforced　with　basalt　fiber-reinforced　polymer　(BFRP)　bars　and　ties.　Nine　BFRP　reinforced　concrete　(RC)　square　columns　were　tested　under　axial　compression.　The　main　parameters　included　cross-sectional　heights,　transverse　reinforcement　ratios,　and　configuration　of　transverse　BFRP　ties.　The　compressive　behaviors　of　BFRP　RC　columns　were　discussed　in　terms　of　axial　load-strain　response,　confined　strength,　and　ductility　index.　The　results　revealed　that　there　was　significant　size　effect　on　the　confined　efficiency　and　ductility.　With　the　increasing　cross-sectional　height,　the　maximum　decreases　of　confined　efficiency　and　ductility　index　were　16.0%　and　18.9%　respectively.　Moreover,　a　meso-scale　numerical　model　considering　the　heterogeneity　of　concrete　was　developed　and　verified　using　the　test　results.　A　parametric　analysis　was　then　performed　to　evaluate　the　effects　of　cross-sectional　height　and　transverse　reinforcement　ratio　on　the　compressive　performance　of　BFRP　tie-confined　concrete.　Finally,　a　design-oriented　stress-strain　model　was　proposed　considering　the　effect　of　cross-sectional　height　and　transverse　reinforcement　ratio.　The　proposed　model　was　validated　using　the　test　results　in　the　present　study　and　literature.