To quantify the influence degree of rebar on chloride diffusion in concrete at the meso scopic level, an indoor physical experiment of chloride natural diffusion into concrete and reinforced concrete specimens under drying wetting cycles in artificial marine tidal environment was carried out. The chloride content distributions in concretes at different diffusion times were measured. The influence of indirect blocking effects of rebar on chloride diffusion coefficient was quantitatively explored based on the meso scopic image technique. Using the indirect and direct blocking effect coefficients of rebar to improve the closed form solution of Ficks second law, a prediction model of chloride concentration in concrete considering the influence of blocking effects of rebar was established. The accuracy of the proposed model was proved by comparing the predicted chloride content in the model with experimental results.