To　study　the　effects　of　water-cement　ratio　changes　and　cracks　on　chloride　ion　transmission　rate　in　cracked　concrete,　RCM　method　was　adopted　to　accelerate　the　diffusion　of　chloride　ion　in　cracked　concrete,　and　the　changes　in　chloride　ion　concentration　and　around　the　cracks　are　inferred　by　finite-element　method.　The　test　results　show　that　as　far　as　prefabricated　cracks　on　concrete　components　are　concerned,　the　width　thresholds　of　two　cracks　on　the　concrete　specimens　with　a　water　cement　ratio　of　0.5　and　0.6　are　0.05　mm　and　0.1　mm　respectively,　the　width　threshold　of　two　cracks　on　the　concrete　specimens　with　a　water-cement　ratio　of　0.4　is　0.05　mm　and　0.2　mm　respectively;　and　the　results　of　numerical　simulation　show　that　the　smaller　the　water-cement　ratio　is,　the　more　significant　effects　of　cracks　on　chloride　ion　transmission　rate　are.　As　a　result,　more　attention　shall　be　paid　to　the　crack　prevention,　repairing　and　strengthening　for　high-strength　concrete.