This　study　investigated　the　seismic　behavior　of　glass　fiber　reinforced　polymer　(GFRP)　strengthened　hollow　rectangular　bridge　piers.　Cyclic　testing　of　reinforced　concrete　(RC)　piers　retrofitted　with　GFRP　was　carried　out　under　constant　axial　loading　and　lateral　bending.　The　failure　characteristics,　flexural　ductility,　dissipated　energy,　and　hysteretic　behaviors,　were　analyzed　based　on　experimental　results.　A　simplified　GFRP-confined　concrete　model　is　developed　by　considering　effective　strength　coefficient　and　area　distribution　ratio　of　GFRP　sheets.　The　results　indicate　that　the　failure　modes　and　damage　region　would　be　changed　and　the　ductility　and　dissipated　energy　of　the　GFRP-strengthened　hollow　rectangular　bridge　piers　were　improved　greatly　but　not　much　improvement　for　the　lateral　load　capacity.　The　analytical　results　of　the　force-displacement　hysteretic　loops　based　on　the　GFRP-confined　concrete　model　developed　in　this　paper　agreed　well　with　the　experimental　data.