To　investigate　the　size　effect　on　compressive　performance　of　circular　concrete　columns　reinforced　with　basalt　fiber-reinforced　polymer　(BFRP)　bars　and　spirals,　nine　geometrically　similar　columns　were　fabricated　and　tested　under　concentric　compression.　The　variables　tested　were　cross-sectional　diameters　(200,　400,　and　600　mm)　and　transverse　reinforcement　ratios　(1.2%,　2.2%,　and　3.3%).　The　results　evidently　indicated　the　size　effect　on　the　confined　strength,　corresponding　strain　and　deterioration　rate　(in　the　post-peak　branch)　of　concrete　core　confined　by　BFRP　spirals.　Specifically,　with　the　cross-sectional　diameter　changing　from　200　mm　to　600　mm,　the　maximum　decreases　in　the　confined　strength　and　corresponding　strain　were　14.1%　and　31.9%,　respectively,　while　the　maximum　increase　in　the　deterioration　rate　was　318%.　In　addition,　the　size　effect　on　confined　strength　could　be　weakened　with　the　increase　of　transverse　reinforcement　ratio.　Increasing　the　transverse　reinforcement　ratio　could　enhance　the　load-carrying　capacity　as　well　as　effectively　increase　the　confinement　strength　and　ductility.　Finally,　a　size-dependent　stress-strain　model,　which　considers　the　size　effect　of　confined　strength,　corresponding　strain　and　deterioration　rate,　was　developed　for　evaluating　the　confined　behavior　of　FRP　RC　columns.