Abstract: The graded structure concrete(GSC) with four different surface-layer thicknesses were prepared,and their diffusion properties were researched by the conducting the Chlorine ion migration rapid test and determining the distribution of chloride ions.And the relationship of chloride ion diffusion coefficient,surface layer thickness and accelerated time were put forward based on the similarity theory.Resultsshow that chloride ion diffusion coefficient of the GSC is reduced with the increase of thickness of the surface-layer,and reaches a stead state finally;secondly,the chloride ion diffusion coefficient in GSC gradually decreases along with the accelerating period increases,and also reaches a stead state finally.