Abstract: In order to overcome the shortcomings of the traditional analytical model of constant diffusion which can not consider the time-varying characteristics of chloride diffusion coefficient, a time-dependent analytical model for the chloride diffusion in circular cross-section concrete is developed. Firstly, the governing equation, boundary conditions and initial conditions for the time-dependent chloride diffusion in the circular cross-section concrete are established in the polar coordinate system. Then, by introducing the equivalent diffusion time, the time-dependent diffusion equation of chloride ion is transformed into the constant diffusion equation, and then an analytical model of chloride time-dependent diffusion in the circular cross-section concrete is developed by combining the Bessel function and variable substitution method. Finally, the proposed analytical model is validated by comparing with the numerical model and the constant diffusion analytical model. Analysis results show that the proposed analytical model is of high accuracy and efficiency, which not only overcomes the limitations of the traditional numerical models whose accuracy and efficiency are largely depended on the spatial discrete grids and time steps, but also overcomes the shortcomings of the constant diffusion analytical models which often overestimate the chloride ion concentration in concrete since they cannot take into account the time-dependent characteristics of the chloride diffusion coefficient. The chloride ion concentration profile in the circular cross-section concrete is between the one- and two-dimensional diffusions, which gradually tends to the one-dimensional diffusion with the increase of the circular cross-section radius and age decay coefficient.