Steel　circular　hollow　section　(CHS)　bridge　piers　have　been　widely　used　in　the　engineering　practices.　However,　end　corrosion　is　one　of　the　most　common　damages　to　steel　bridge　piers,　leading　to　degradation　of　seismic　performance　and　changing　of　failure　modes.　This　paper　investigates　the　seismic　performance　of　the　chloride　corroded　steel　CHS　bridge　piers　and　proposes　a　method　to　predict　its　lateral　ultimate　strength　under　the　transverse　cyclic　loads.　Firstly,　the　multi-scale　finite　element　(FE)　models　of　the　CHS　steel　bridge　pier　are　developed　considering　both　the　local　buckling　and　the　end　corrosion,　which　are　calibrated　against　the　previous　test　results.　Subsequently,　the　effects　of　the　characteristic　parameters　(i.e.,　the　corrosion　conditions　and　the　column　parameters)　on　the　failure　modes　and　the　horizontal　ultimate　strengths　of　the　corroded　steel　CHS　bridge　piers　are　investigated,　and　then　the　sensitivity　of　the　parameters　is　quantified　using　the　Sobol　method.　Finally,　a　method　is　presented　for　estimating　the　ultimate　strength　of　the　end　corroded　steel　CHS　bridge　piers　under　the　horizontal　cyclic　loads.　Results　show　that　the　end　corroded　bridge　piers　exhibit　more　significant　stress　concentration　when　comparing　with　the　uncorroded　bridge　piers.　The　buckling　half-wavelength　is　influenced　by　corrosion　parameters,　and　the　buckling　position　changes.　The　ultimate　strengths　of　end　corroded　bridge　piers　are　reduced,　which　is　more　sensitive　to　the　corrosion　rate.　The　proposed　theoretical　method　to　predict　the　ultimate　strengths　of　corroded　steel　CHS　bridge　piers　is　accurate　enough　with　errors　less　than　10%.