Abstract: The corrosion of reinforcing bar induced by chloride ion is the main reason for the properties degradation of concrete structures under the chloride erosion environment,at present,the study on chloride ion diffusion properties almost takes free chloride ion as the object,the diffusion properties of total chloride ion in concrete has rarely been studied. The diffusion properties of free chloride ion and total chloride ion in concrete were further studied by natural diffusion method in this paper,the effect of water-binder ratio on chloride ion diffusion properties was investigated,the time-dependence of chloride ion diffusion coefficient was taken into consideration,the relationship between the effective chloride ion diffusion coefficient and the apparent chloride ion diffusion coefficient was established,which has laid a foundation for more scientific durability life prediction of concrete structures under the chloride erosion environment.