In　order　to　analyze　the　effect　of　chloride　corrosion　on　seismic　performance　of　bridge　structures,　a　methodology　is　proposed　to　evaluate　the　seismic　risk　probability　of　offshore　bridges　considering　the　material　degradation　in　marine　environment.　The　numerical　model　of　a　continuous　concrete　reinforcement　bridge　is　established　by　finite　element　software　of　OpenSees.　The　random　samples　of　longitudinal　reinforcement　diameter,　yield　strength,　stirrups　diameter　and　cover　concrete　compressive　strength　of　corroded　piers　under　different　service　time　are　obtained　based　on　the　probabilistic　method.　The　set　of　samples　combining　ground　motion　and　bridge　is　formed.　The　damage　states　capacity　of　bridge　piers　is　analyzed　by　the　Pushover　analysis.　The　incremental　dynamic　analysis　of　bridge　is　carried　out.　The　seismic　vulnerability　analysis　is　carried　out　for　each　component　and　the　whole　system　of　the　bridge.　According　to　the　site　type,　the　seismic　hazard　curves　of　bridge　structures　in　different　service　time　are　obtained　by　the　equal　transcendental　probability　theory　and　the　existing　seismic　hazard　model.　Monte　Carlo　method　is　used　to　generate　random　samples　of　ground　motions　in　different　service　time.　The　seismic　risk　probability　of　the　offshore　bridge　can　be　evaluated　based　on　the　seismic　vulnerability　analysis　and　the　seismic　hazard　evaluation.　The　results　showed　that　the　performance　of　reinforced　concrete　degraded　and　became　progressively　worse　with　advancing　service　time.　The　corrosion　of　stirrup　resulted　in　a　significant　decrease　in　shear　capacity　of　the　pier.　The　failure　mode　of　corroded　pier　is　changed.　The　influence　of　shear　deformation　should　be　considered　when　establishing　the　finite　element　model　of　corroded　pier.　Considering　the　degradation　of　material　properties　caused　by　chloride　ion　erosion,　the　seismic　risk　probability　of　longitudinal　and　transverse　damage　of　bridge　system　decreases　with　the　increase　of　service　time.　The　risk　probability　is　about　25%　higher　than　the　bridge　without　material　degradation.