One　of　the　main　reasons　for　corrosion　of　reinforced　bars　is　the　superfluous　chlorine　ion　penetrating　into　the　reinforced　concrete.　This　article　investigated　and　measured　the　reinforced　concrete　bridges,　which　have　been　put　into　use　for　10　years　along　the　seaside　highway　in　Qinghuangdao　area.　The　results　show　that　there　exists　many　damages,　such　as　concrete　cracks,　reinforcement　corrosion　and　protection　layer　faking　off.　The　measurement　results　show　that　the　corrosion　thickness　of　chlorine　ion　exceeds　the　thickness　of　protection　layer　in　some　places.