<jats:p> A method to link one-dimensional (1D) and two-dimensional (2D) diffusion coefficients of sulfate ions in concrete is proposed. The method was established on the basis of 1D and 2D diffusion tests for different concrete strengths, different concentrations of sodium sulfate solution and different immersion periods. Based on the test results, a new 1D diffusion coefficient model, related to concrete strength, sodium sulfate concentration and immersion period, was established. It was found that 2D sulfate diffusion was not simply the superimposition of two 1D diffusions. Under the multi-factor conditions, the average diffusion coefficient in the 2D case (D<jats:sub>2D</jats:sub>) was found to be approximately 1.33 times that of the 1D case (D<jats:sub>1D</jats:sub>). Based on the 1D diffusion coefficient model and the D<jats:sub>2D</jats:sub>/D<jats:sub>1D</jats:sub> = 1.33 relationship, a new 2D diffusion coefficient model was developed. Complying with Fick's second law, based on the 2D diffusion coefficient model established, the sulfate ion concentration at each point under muti-factor conditions for 2D diffusion could be obtained, which also verified the proposed diffusion coefficient model. </jats:p>